Most people probably don't realize how bad this really is, and how worse it's becoming.
For instance, some time ago there were news about a famous patent troll (Lodsys) threatening to sue *individual* iOS developers over the technology used to, get this, 'click a button on an application and be taken to a web site' (e.g.; every 'Buy Now' button in existence). *Everyone* does this in one way or another, and there is obviously prior-art.
The fact that there is prior-art (and that the patent is therefore invalid) is absolutely meaningless, however: to prove that there is prior-art, you must do it in a patent friendly court of law, and be willing - and, more importantly, able - to spend a minimum of hundreds of thousands of dollars to fight for your cause. Because you will be defending yourself in a jurisdiction that has a clear bias to upholding existing patents, there is the very real risk of losing, in which case the whole shebang falls down on you!
Small developers had no way to fight this, so they had no choice but to settle. Some reached out for help to the ones who *could* fight Lodsys: Microsoft, Apple and Google. The problem is that LodSys is a company exclusively dedicated to buying patents and then extracting royalties from others. As such, all the giants had already signed deals with Lodsys for patents in bulk - with a clause in the contract that prevented them from litigating with Lodsys. So their hands were tied.
Lodsys then started going after small PC developers.
Now get this: if you settle with Lodsys to avoid being sued, even if the patent is later overturned, you still have to keep paying them royalties anyway. If you don't settle, you get sued.
This is nothing but a legalized extortion racket.