As google maps shows there are serious limits to what you can do with the data. It quickly becomes disorganized jumbles of spam, inaccuracies, and miscategorized information.

Once enough data is collected, and then cleaned up, it may be possible to make something useful out of it, but given location based examples, you have to rate the quality per square inch of the data, and that usually doesnt hold up outside of big cities, and is skewed by the users themselves who do not represent a fair statistical sample.