It may also have something to do with the way European Patent Law is framed. As I understand it (and I'm not a Patent Attorney), it is quite difficult to get a patent here: An applicant has to prove that there is no prior art and that what they are trying to patent is both genuinely innovative and actually realisable. Any subsequent discovery of prior art will result in the patent being revoked through a pretty speedy tribunal process. That seems to contrast starkly with the apparent picture of the US Patent Office granting patents with next to no checks on prior art or practicability and then relying on people who might want to use (or already be using!) the idea to attack the patent through an expensive legal process which uses 'standard' courts (and all the costs they entail) rather than specialist tribunals.
Lest it sound that I am rabidly pro the European situation, I'd like to be clear that it brings its own problems: Since the costs and the problems are here loaded on the applicant's side, it can be quite difficult for the individual inventor / innovator to protect his or her idea whilst bringing it to market. So, my comment on Jason's comment would be that perhaps it is the US patent system - with all its obvious faults - that
generates the perceived greater creativity.
Somewhere in the middle ground there has to be a better solution, but better minds than mine are failing to find it.
In the meantime, large companies like Dell, HP et all might do well to instruct their legal departments to monitor the patents being granted and challenge anything that looks like it might conflict with what they are doing / planning to do. A few serious pre-emptive strikes might give the patent squatters pause for thought.