The internet introduced "wisdom of the crowd". Under certain conditions the crowd is more correct in estimating and predicting things.

So what is more natural to use social media such as blogs and Twitter for predictions!

http://www.newscientist.com/article/mg20627655.800-blogs-and-tweets-could-predict-the-future.html?full=true

Here is a site that is actually trying to do exactly this:

https://www.recordedfuture.com/how-it-works.html

Some problems might arise here. One of the conditions for "wisdom of the crowd" is that individuals shouldn't affect each other so much that the result is changed significantly. Blogs and tweets are constantly referring to other blogs and tweets so they are really affecting each other. So can we really rely on these results? Hard to predict, the future will tell...

Finally, we have the well known contradiction of predicting the future and being able to change our destiny. If I can predict for instance my own death in a car accident I will not go by car that day. My prediction would be wrong.