The ideal tool for robbery has apparently become Foursquare, the iPhone app for sharing your whereabouts with your 900 closest friends. And your least discreet buddy might be in league with the thieves. Here's how to avoid being that friend.

The new website is designed to illustrate the criminal potential of Foursquare. It shows Foursquare users tweeting the fact that they are no longer at home, and thus that their valuables are potentially vulnerable to thieves. The site has certainly gotten people's attention.

What's especially scary is that even if you are careful about broadcasting your location, your "friends" can still screw up your security. We'll explain below, and throw out some other important "Don'ts" for this latest social networking technology to finally reach your most annoying buddies:

Don't check in from a friend's house: We realize you want to brag about the party you're at, or maybe are desperate to enliven it with some fresh blood. But do not do this, because it means giving up their address, and if your friend ever tweets about being on vacation, the savvy thieves will know exactly who to burgle next.

As PleaseRobMe puts it (via Agency Spy), "Now you know what to do when people reach for their phone as soon as they enter your home. That's right, slap them across the face."

Don't check in from work: This is annoying and pointless. Your friends know where you work. And your public is not impressed that you're gainfully employed. Some people think it's fun to try and become "mayor" of the office, i.e. the person who is there the most hours. (We're looking at you, CNET.) But becoming mayor of the office just telegraphs, "I have an utterly perverse definition of 'accomplishment.'" (Possible exception: If you work at Foursquare like these guys at left, via Scott Beale.)

Don't become Foursquare friends with pure Facebook 'friends:' We first saw this tip on the website Old Media New Tricks, and it's especially relevant when you start thinking about crime. If you only "know" someone through Facebook or Twitter, they shouldn't have access to your location. Your contact might look like a sexy young thing in a bikini on Facebook; in real life you might be dealing with a nasty ex-con looking for leads for his next big score — including any data you share about your real-life buddies.

Don't get all anxious about who Foursquare friends you: As former Valleywag Nick Douglas wrote in 2008 about the similar service Dodgeball, this sort of social networking can get overwhelming fast, in part because of the physical aspect. "One night, two people Dodgeballing from a bar drew a crowd of thirty," he wrote. "And god did the parties get awkward when one person realized they were the only one not getting a text message when their friend walked in the room."

The instinctive reaction to this sort of social tidal wave is to retreat. So if someone unfriends you, or doesn't accept your invite in the first place, get over it.

(Top pic: Foursquare and Dodgeball creator Dennis Crowley, via his Flickr; robber pic by Eben Bleep; Foursquare office by Scott Beale on Flickr)