What happens when the tools you use to find love, are the ones you use to find vengance for a broken heart? (Pablo Blasberg/Ikon Images/GETTY IMAGES/COLLECTION MIX: SUBJECTS RM)

So, you met online. How sweet.

Or perhaps you didn’t meet online, but kept up the relationship via Web and mobile. But now the relationship is over and Valentine’s Day has taken on a new flavor for you or your ex.

Except privacy is not what it used to be, especially on the Internet. The same sites and tools that make it possible for you to keep track of your friends’ whereabouts and find love are also the same tools that make it possible for people you'd rather not to track you (say, an ex-lover) anywhere you go. With the proliferation of new geo-location technologies and the constant efforts by sites like Google and Facebook to make even more of our personal information available in searchable formats, our profiles and social data are increasingly fair game for anybody with a smart phone.

On Valentine’s Day, that combination of availability and access is especially enticing.

Now that Facebook has flipped the switch on Timeline for its 800 million users, our entire digital lives are now laid out, in neat chronological order, for our Facebook friends to review at their leisure. Beyond that, Facebook also simplifies the process for voyeuristic "Facebook stalkers" by encouraging users to self-identify the defining moments of their lives — from engagements to marriages to the arrival of new children. If you haven’t blocked an ex-lover from viewing your Facebook page yet, they will continue to have access to your photos, videos and status updates from your new relationships. And those photos that you think you deleted? Facebook acknowledged that it might be possible to access these deleted photos on the Internet.

Across the Internet, the Social Graph is being replaced by the Interest Graph, as outlined by ReadWriteWeb’s David Rogers. This Interest Graph maps our relationships with objects as well as with people. That means there are even more ways for the jealous Valentine to keep tabs on a loved one.

Pinterest, which encourages users to “pin” photos that represent their moods and inspirations, has exploded into prominence, becoming the fastest site to hit 10 million monthly users ever. If, before, you used to “Google” your love interest to see what they’re up to, you can now see what he or she finds interesting by checking out their pins. It’s quite likely that your former love interest is pinning photos of new outfits, new additions to their home interiors and maybe even dream photos of their perfect wedding. Imagine showing up on a date armed with that information to convince your love interest that you’re Mr. or Mrs. Right.

Our social networking data, which used to be relegated to the desktop, is now making its way to our smart phones. Many of the newest social networks — such as Path, Instagram and Color — are “mobile first, Web second”, networks, as termed by venture capitalist Fred Wilson. The newest dating sites, like Blendr, are also mobile-centric, taking advantage of geo-location data to show you possible matches around you. Which, of course, raises a whole host of questions because we have information stored on our mobile devices — such as our address books and text messages — which we probably never accessed on our desktop. Path ran into exactly this issue last week, when it became public that the company was uploading users' address books — in their entirety — to its network.

Get ready for even more blurring of the line between our real-world and digital-world selves and the confusion that it could bring to relationships. Consider KLM's Meet & Seat program for flyers, which encourages travelers to check out the social networking profiles of fellow travelers. Before you even purchase your ticket, you can log in with your Facebook or LinkedIn account and check out the profiles of the flyers sitting near you on a specific flight. While this seems to have greatest application for socially-minded business travelers headed to a conference, it’s easy to see how it could be used by a new generation of Talented Mr. Ripleys to find new objects of obsession while on vacation.

There is a bigger picture here. Lurkers, trolls and stalkers have always populated the Internet. However, technology is now converting everyday Internet users into stalkers and lurkers as well, simply because it is so easy and the information is so enticing. (How many times would you check out the Facebook profile of a former lover if you could?) As a society, we are at the cusp of redefining the very notion of personal privacy. To work - and to work well - social networking sites and smart phone apps need access to detailed, personal information about our lives. To turn our personal lives upside down, however, all it takes is for some of this data to get out into the wrong hands at the wrong time.

View Photo Gallery: From neurons to nanobytes, scientists are discovering more about why we fall in love, while technologists are discovering new ways to help us find the loves of our lives.

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