Excellent post from Frans Bouma. It is way too long to copy here, but here is my favorite part (about software patents):

This is also the reason why I think software patents are a bad thing: they do not help to get an advantage over a competitor, but they do give a false feeling of having that advantage, which makes patent holders to focus on their patent instead of their USP's which really matter. In the end the customer, the end user, is the one who really looses: he has to wait till the competition has worked around the patent, and till then he probably won't have the product he wants, because the patent holder is not forced to focus on USP's which will bring that product.