Being accused of a precrime is one thing to be concerned about. It's happened to quite a few people. People who planned an event similar to "Improv Everywhere" in London were captured and detained before they could do something which was not even illegal... An Irish guy got questioned for a solid 12 hours and sent home for an innocuous tweet. Another person was detained and had his home trashed for quoting a movie on Facebook. This happens all the time. Imagine if you are a writer for a mystery novel, you want to do some research, and then someone close to you dies. Now your research queries are going to be used to make you look guilty. Yeah, an 'innocent' man has nothing to fear from the law, except they do, as you can clearly see if you ever have heard of http://www.innocenceproject.org/.