You'd think this iPhone app would be a juggernaut from booty call heaven. You'd be wrong. One man's cautionary tale from the trenches of tech-savvy casual sex.

First, the good news: The iPhone Facebook app allows you to sync the contact info in your friends' profiles with your personal address book. Now, you have everyone's phone numbers and email addresses in the palm of your hand—it even adds profile pics!—increasing your booty call quotient manifold.

Now, the bad news, in the ominous subject line of a tip email: "Facebook knows your one night stands."

You know how when you meet someone at a bar or alcohol-soaked party, sometimes you put him in your phone without a last name? And you already have a Jonathan, so this guy will be "Jonathan Pencil Factory," because that's the bar where you met him. And it was a moonlit night with too many margaritas, and your fingers were busy with activities far more urgent than tapping a new entry into your contact list, so when you finally had a second to type him in, it ended up more like "jonthann pencil factry blueyes." (Sometimes you need a defining feature, too.) Sometimes these besotted acquaintances turn into true love. Sometimes they become friends. But most are nothing more than a single night of your life—and a quiet chuckle every time you scroll past their names in your phone book, months later.

Until you sync your iPhone with your Facebook. And then you will be forced to look your every unwise sexual decision in the eye, again, in full color and with full names! Or, so says a tipster who explains that syncing his iPhone with Facebook resulted in deep emotional disturbance:

contact entries who you may or MAY NOT be friends with on facebook, contact entries whom you have blacked out of your memory, contact entries who you drunkenly entered while 5 long island iced teas deep into a gay pride party... have been unveiled. the facebook app has linked these misspelled, drunken entries to actual people on facebook (through some sort of secret phone number search, i presume), finally unveiling the true identity of the trolls that you had all too conveniently erased from your memory. i first noticed this when i accidentally opened up a "jerremmy pool party," to find that there was now a facebook link to his name. i had no recollection of this jerremmy, but now i am informed that he is an aspiring actor/bartender living in hell's kitchen, with a gaggle of friends in common, but more importantly—ugly as SIN. these people run the gamut—people i am well aware of making out with, people i bedded and forgot, people i vaguely remember my roommates teasing me about the next morning, but the scariest ones were the handful people i don't even remember meeting—people that had otherwise been dead to me.

Chilling. Our tipster also grapples with the Brave New World of non-anonymous one-night-stands:

perhaps i am asking for this very unwelcome re-introduction to my past indiscretions, perhaps i deserve the embarassment of facing the true indentity of my blackout makout. but another, less sober part of me thinks that this is yet another way in which the cyber-stalking era is ruining lives, and waging war on the world of anonymous intimacy. a one-night-stand should be just that, but in 2010, it's more like just the beginning.

"Just the beginning," he said with a shudder, imagining a hideous dystopia where sex would lead to relationships. Where every set of genitals belongs to a human. With feelings. And family. And Favorite Quotes and Mutual Friends.

Update: Is this phenomenon real? None of our non-Facebook friend contacts synced. But the tipster stands by his story, and some commenters say variations on the iPhone-Facebook sync dilemma has happened to them, too. [First pic via]