I'm not sure. I just read SuperFreakonomics and IV is featured (quite positively, I might add) in the book.
According to the authors, IV exists to provide a mass market for IP by acting as a clearinghouse. They purchase patents (from anyone, but that does include small-time engineers/inventors without the capital to develop their creation) and solicit other companies to license them. They also do a fair bit of inventing themselves (including some awesome environmental engineering devices intended to stop global warming and reduce the effects of hurricanes!) so it's not clear to me that they exist *only* to troll.
That being said, it *is* clear that their primary source of income is the licenses from their patents and it's *not* clear what percentage of their profitable patents are things invented in house or externally.