Washington lawyer William Wilhelm knows from experience that not everybody loves his BlackBerry as much as he does.

"I once had a date become apoplectic because we were in the airport terminal before vacation, and I did the one final BlackBerry check," Wilhelm said. The girlfriend was fed up with a relationship punctuated by Wilhelm fiddling with the wireless device to check hundreds of e-mails a day.

BlackBerrys, sometimes referred to as CrackBerrys among addicted adherents, make e-mail portable, available anytime and almost anywhere. Airline delays become office time. An elevator ride becomes a chance to dash off a reply. A companion's restroom trip at a restaurant provides just enough time to close a deal electronically.

For some, like Wilhelm, the pocket-size devices have created a borderless world of new opportunities for multitasking. BlackBerry -- and a growing number of cell phones like them that come with tiny keyboards -- have made it easier and more tempting than ever to sneak in work during personal time, and personal messaging at work.

But as instant e-mail devices accelerate the cadence of work life, there are increasing complaints that they whittle away at time that people once used to give undivided attention to family or co-workers, or to find solitude on the beach or during the daily commute.

E-mail on the go also has raised new questions of electronic etiquette. Most people have learned to shut off their portable phones or set them to vibrate silently during business meetings and social events. There's no such consensus yet on proper behavior for those who silently, relentlessly, punch out BlackBerry messages with their thumbs.

In a recent survey by Harris Interactive commissioned by wireless provider T-Mobile USA Inc., 15 percent of wireless-device users said they have e-mailed from a restroom, 19 percent while eating in a restaurant, and 21 percent while talking to friends or family.

BlackBerry, introduced in 1999, is the most prominent example of a broader wireless e-mail phenomenon. About 1.6 million BlackBerrys are used in the United States, according to the maker, Research in Motion Ltd. of Ontario, Canada. In addition, there are more than 14 million "smart phones" -- mobile phones with keypads and Web browsers -- among the 169 million cell phones in use in the United States, according to Instat/MDR, a market research company. The firm predicts the number of smart phones will increase 44 percent a year over the next five years.

At $200 to $500 for recent models, plus monthly connection charges of about $40, BlackBerrys, Treos and other e-mail-friendly devices are still used mostly by highly paid professionals. Through wireless carriers, Research in Motion sells BlackBerrys to law firms, health care companies, real estate agents and government agencies.

Increasingly, wireless e-mail gadgets are being marketed to a broader audience. T-Mobile's flip-top Sidekick is popular among young consumers even though its price approaches that of a BlackBerry. This week, AT&T Wireless introduced Ogo, a $99 wireless device that offers e-mail and messaging service for $17.99 a month.

As prices start to fall, more and more people will use such handhelds as miniature substitutes for their desktop computers, said Neil Strother, a senior analyst with Instat/MDR.

The proliferation seems to have a viral effect -- accelerating the general pace of business, compelling others to get things done even faster.

"There's competitive pressure if you're not responsive to e-mail," said Wilhelm, who is a telecommunications lawyer. He acquired a BlackBerry early last year because his clients and colleagues -- all of whom had some type of wireless e-mail device -- began expecting immediate responses.

BlackBerrys also have changed the dynamic of many business meetings.

Doug Poretz, a public relations executive at Qorvis Communications LLC in McLean, says he often sees employees hunched over, typing below the table. "I have mixed feelings about it," he said. "If they're checking on client business, that's okay." But for all he can tell, his co-workers may be making weekend plans.

In a Washington law office, attorney Chris Rhee often participates in meetings in a conference room walled with thick concrete slabs that block most wireless signals. Around him -- in the middle of meetings -- attorneys lean back and wave their BlackBerrys in the air, trying to catch a stray signal through the window.

Barbara Harsha, executive director of the Governors Highway Safety Association, said that at one recent conference, she slid her BlackBerry out during a droning presentation and under the table typed out an e-mail to a colleague: "This speaker is just awful." When she looked up, the man seated next to her was doing the same thing.

Such activities can unnerve others. "I've been in depositions where opposing counsel will pull it out and check it," said Brian Moffett, a Baltimore litigator who puts his Treo -- a cell phone with an oversize screen and keypad -- on vibrate and doesn't allow himself to glance at it in meetings. "It raises issues with me, like jeez, someone thought it was important to show up to the meeting but not enough to pay attention."

Jacqueline Whitmore, a technology etiquette consultant for Sprint, said, "As a speaker, you know who's not paying attention. Their eyes are not on you. That means they're disinterested. That's when you start to feel edgy."

James L. Balsillie, co-chief executive at Research in Motion, the BlackBerry maker, is unapologetic. "Some would say we've subverted meetings, but I would say we've liberated people from boring meetings," he said. It puts the onus on the speaker to be interesting, he said.

BlackBerry-style technology exacerbates the modern habit of multitasking, said JoAnne Yates, a professor of communication and organizational studies at the Sloan School of Management at Massachusetts Institute of Technology, who is studying the effect of BlackBerry use on society. "That is scary, because we're getting too used to not paying attention to one thing at a time, but splitting it on many things."

The BlackBerry also has tethered some people closer to work. "While people keep talking about wireless as liberating, in fact there's the other side, which is that we're drawn in to being accountable wherever we are and always answering," said Sherry Turkle, director of the MIT initiative on technology and self. "You never know when you're not working. You're losing time to quietly reflect."

Since getting a BlackBerry, Jonathan Adkins started sending his boss, Harsha, late-night e-mails.

"I take it with me to the gym. I keep it on my belt, even while I'm working with a trainer," said Adkins, communications director at the Governors Highway Safety Association. "In this country we don't have that much downtime. It's probably not good for our mental health to do business at 10 o'clock at night, but it takes a lot of willpower not to, especially as everyone else does it."

Harkins Cunningham LLP handed out BlackBerrys to its lawyers this year, but not before extensive internal debate. David A. Bono, a partner at the firm's District offices, said one senior partner feared that lawyers would be distracted by their BlackBerrys in meetings and thus would make mistakes. But the competitive urge to be available at all times won out.

Now, Bono said, his BlackBerry finds its way onto the dinner table in a restaurant, where he sneaks a peek at it when it flashes. "I just roll the wheel," he said, referring to the scrolling mechanism on the side that allows him to see who has sent a message. "I try to be very discreet about it and not look at it very much."

Some say they find it calming to keep continuous tabs on the office.

"It's the perfect productivity tool for anxious professionals," Wilhelm said. Then he wondered out loud: "Does the BlackBerry make someone more neurotic, or does a neurotic person find that the BlackBerry comforts them?"

People write e-mail anywhere with BlackBerrys.