To be honest, based on what I've heard about it my impression is that the way the US patent office handles patents is a large part of what enables patent trolls (here used as an umbrella term for all patent abuse discussed so far) to do their thing.

Namely that it's relatively easy to get a patent, and that the validity of it is then tested in court. However, often the threat of going to court is what is abused by patent trolls.

In most other countries getting a patent is the hard part.