Some people still fail to understand that not any old thing should be shared on sites like Foursquare, for the mere reason that it might be spread much farther than they first thought. Fourtrace highlights such a fact perfectly, as it will let anybody see exactly which parts of the information that they are sharing on Foursquare is being picked up by Twitter, and relayed from there.
The site features a plain search interface that will let you provide the username of any Foursquare or Twitter user you want to trace, and a Google Map for the contextualization of search results. At no point are you required to supply personally identifiable information of any kind.
By letting people know about these things that are being made public on something as widespread as Twitter when they are checking in and out of places, Fourtrace has the power to make people aware of the risky side of social sites. Most individuals understand that from the beginning, but then again there are some who can only learn things the hard way.
Fourtrace.com In Their Own Words
Trace your friends from Foursquare.
Why Fourtrace.com It Might Be A Killer
It is a great way to become aware of how much you are really revealing when using the most popular social services today.
Some Questions About Fourtrace.com
What can you do with the results that are provided? Can you have them exported? 
