DARPA conducted a contest whereby they put up 19 balloons such as the one pictured above. These balloons were spread across the entire continental USA. Then they offered a $40,000 prize to the first group who could give the locations of all of the balloons.
Students from MIT (the Massachusetts Institute of Technology) won the prize. They used the Internet, Facebook and Twitter to recruit spotters all over the country. Then they distributed the potential prize money to whoever spotted balloons, creating a financial incentive. They were incredibly successful at doing so.
The whole idea is to use this methodology to find things like terrorists, missing planes, downed satellites or whatever that needs to be found in the US without spending a lot of money in fruitless searches. It is an algorithm for using social networks to find the needle in the haystack.
So social networks do have a use -- other than being an all inclusive time and life waster for connected young folk.