One of the best (worst) aspects of software patents (depending on your viewpoint) is that one may infringe them accidentally too easily. As has been noted many times before, software patents, for various reasons, tend to be overly abstract and generic. This means that the probability that you genuinely invent a solution to a problem, and that the said solution then infringes a third-party owned patent, is notable.
This is the reason why Big Corporations push software patents heavily. If you have a big collection of patents, any randomly chosen software company with a high propability infringes at least some of them. This opens an avenue for ligitation. Therefore, patents turn into abstract warfare, and it is then the number and extent of patents which counts.
Because a Big Corporation can acquire a larger number of patents than a small enterprise, Big Corporations win the arms race. Therefore, it is logical for Big Corporations to be proponents of software patents; and for individual software engineers and small enterprises to be against them.
In the same way as medieval kings and modern countries must have armies, so must software companies nowadays and in the future have patents. The king with bigger army wins. The corporation with larger patent portfolio wins. So, software patents bring [not-any-more-so-much] a change in the rules of the game, and it depends on your position, whether the change is for good or for bad.