1) They last a VERY long time as measured in "Internet time"
2) It's very hard to find examples of GOOD software patents. They tend to either cover too much (one click shopping), or they are really just math expressed in code (encryption and compression algorithms).
3) They are easy to abuse, since it takes so little time to produce them and the people who grant them don't really understand them.
I'd say their legal status in current intellectual property law (in some countries) is what makes them special.
The widespread abuse of patents has IMO flipped the original rationale for having them (to promote the progress of Science and useful Arts) into tools that discourage innovation and experimentation.
Whether an idea is novel seems relative to who you are talking to in my experience.
That's one of the significant problems with (software) patents. Someone who thinks an idea is novel gets a patent on it and uses it to attack people who knew it wasn't.
If there's anyone on the planet who finds an idea obvious, it shouldn't be patented.
