The liberal group Media Matters for America waged a sustained campaign targeting Glenn Beck’s advertisers that drove many off Beck’s highly rated Fox News program and ultimately ended Beck’s association with the cable network. Similar campaigns drove Don Imus and Dr. Laura Schlessinger from the air after they made inflammatory comments. (Chris Keane/Reuters)

Dan Sileo just got a taste of what might be called the Rush Limbaugh Effect. On his sports-talk radio program in Tampa last week, Sileo enthusiastically endorsed the Tampa Bay Buccaneers’ interest in a trio of free-agent players. Maybe a bit too enthusiastically.

“If they got those three monkeys, I’m good,” Sileo said about the players, all of whom are African American. “I’m ready, man . . . I want those guys. Those guys are great players.”

That was Monday. By Tuesday, Sileo was gone, fired by WDAE-AM (“The Sports Animal”), where he’d worked behind the microphone for nearly 15 years. The station, owned by radio giant Clear Channel Communications, has declined to talk about Sileo’s dismissal.

Nevertheless, in the wake of the furor over Limbaugh’s denunciation of Georgetown law-school student Sandra Fluke last month, Sileo’s firing suggests to many that something has changed about the sensitivities of talk-radio stations. A medium built on pushing the limits of acceptable speech appears, once again, to be reassessing just where those limits are.

Limbaugh, the nation’s most popular talk host, is still being battered by liberal activists and others for calling Fluke “a slut” and “a prostitute” for her advocacy of mandatory insurance coverage for contraception. Dozens of advertisers have declared Limbaugh’s program a no-go zone, at least temporarily. This has left his syndicator, Clear Channel-owned Premiere Radio Networks, to fill some of the commercial breaks on his program with freebie public-service ads.

The fallout appears to have less to do with listeners’ reactions to his derogatory comments — there’s no evidence that Limbaugh’s audience has abandoned him in the past two weeks — than with advertisers’ nervousness about being associated with something “controversial,” which is precisely what political talk radio strives to be.

The medium has endured many such controversies before, of course. The influential Joe Pyne pioneered “confrontational” radio in the 1950s, and Limbaugh got his start in the mid-1980s as a replacement for Morton Downey Jr., whose shtick was insulting callers to his program.

But some in the talk business suggest things are different now.

For one thing, the Limbaugh flap has demonstrated anew how individuals and interest groups, such as the liberal Media Matters for America, can gin up and sustain outrage via social media (in Limbaugh’s case, President Obama’s consoling phone call to Fluke probably helped fan public revulsion, too). The group waged a sustained campaign targeting Glenn Beck’s advertisers that drove many off Beck’s highly rated Fox News program and ultimately ended Beck’s association with the cable network. Similar campaigns drove Don Imus and Dr. Laura Schlessinger from the air after they made inflammatory comments.

For another, some see the radio industry as uniquely vulnerable to sustained pressure. A long period of consolidation has left industry giants such as Clear Channel with a vast portfolio of stations but also deeply in debt, making them extra sensitive to anything that might disrupt their revenue (for the record, Premiere has issued a statement generally supportive of Limbaugh).

“In my view, when increasingly aggressive, organized pressure groups meet today’s increasingly gutless corporations, the pressure groups will win every time,” says John Mainelli, a veteran broadcast-industry consultant who put Limbaugh on his flagship station, WABC in New York, in 1988. “Media corporations are now so big that they think no one person or show, even Rush, is worth suffering major PR grief” from boycotts or lawsuits.

Clear Channel has become so large, says Mainelli, that even a titan like Limbaugh is no longer considered indispensable.

Advertiser nervousness over inflammatory or polarizing commentary clearly goes beyond Limbaugh. The trade publication reported last week that Premiere has circulated to station managers a list of 98 blue-chip advertisers that had requested their commercials not air during programs “that you know are deemed to be offensive or controversial” or are “likely to stir negative sentiments from a very small percentage of the listening public.” The programs include not just Limbaugh’s but those hosted by many of the leading conservative talkers on the air: Sean Hannity, Mark Levin, Glenn Beck and Michael Savage.

Such edicts indicate that “all of talk radio, or all of conservative talk radio, is being tarred” in the reaction to Limbaugh, said Michael Harrison, the publisher of Talkers magazine, which covers the talk-show business. Harrison sees the damage to Limbaugh as “a short-term dent” that will harm Clear Channel’s cash flow for a month or two. But the episode may have a lasting impact as advertisers reconsider the value of being associated with any kind of controversial material, he said.

If so, that puts conservatives under a cloud, since the most popular figures on talk radio are to the right. Conservatives such as Limbaugh, Hannity and Laura Ingraham hold the top five slots on Talkers’ magazine’s latest ranking of the medium’s biggest stars, and 11 of the first 20 spots (the rest are liberal, independent or non-partisan hosts).

The backlash against Limbaugh, in fact, has set off a counter-backlash from conservatives who have denounced liberal figures such as radio-TV host Ed Schultz and comedian Bill Maher for making disparaging comments about women in the past. MSNBC, which carries Schultz (and has run numerous segments about Limbaugh), has stood by him, as has commercial-free HBO, which airs Maher’s “Real Time” show.

“At a time when Obama’s [approval] ratings are falling, it sure looks like liberals are trying to knock conservative talkers off the air to help get Obama reelected,” says Tim Graham, director of media analysis for the conservative Media Research Center. “But there’s certainly the possibility that these campaigns could sour sponsors on all of commercial talk radio. Conservatives have more to lose in that scenario.”

The “liberal success” in targeting Imus, Beck and Schlessinger, Graham adds, “has every conservative host watching his back.”

The new climate, says talk-show consultant Randall Bloomquist, is evident in a slogan used to promote former Arkansas Gov. Mike Huckabee’s new syndicated radio program: “More conversation, less confrontation.” Bloomquist knows from direct experience how unforgiving corporate radio can be. In 2005, he was fired as program director of Limbaugh’s Washington affiliate, WMAL-AM (then owned by the Disney Co.) along with host Michael Graham after Graham made disparaging comments about Muslims on the air.

The conundrum for talk radio may be how to stay provocative — its stock in trade — without inciting outrage.

It’s a fine line, acknowledges Valerie Geller, a talk-show talent coach, but it’s not impossible to walk it.

“Great talk radio is based on charismatic, interesting personalities, along with great storytelling, new information, and it works especially well when there’s humor,” she writes via e-mail. “We do enjoy freedom of speech in this country, but using that freedom wisely is the responsibility of each host and producer. Remarks that are racist and offensive will turn audiences (and sponsors) away . . . I’m constantly reminding hosts and producers: ‘Be aware of what you’re saying. The public airwaves are not your living room.’ ”