Look Who’s Stalking: 10 Creepiest Apps For Phones, Facebook, More
An app that introduced the idea of the "might go," Crowded Room is like a Foursquare check-in, but with a twist: It’s a check-in for the future, and you may or may not even decide to show up. The app lets you look up people who have similar prospective plans (if they've allowed the plans to be viewed publicly) and message them.
The premise is that you might meet up with them because you have things in common -- you might frequent the same places or have a mutual friend. But is that a strong enough link to open yourself up to an encounter with a potentially dangerous stranger?