That's how it works :-(
> Does this seem ridiculous to anyone else: you have to prove you *didn't* infringe on a patent?
Ridiculous? Yes. But unfortunately, that's how it goes.
The courts have taken the position that the USPTO has a clue. They have decided that, as the USPTO has examined the patent application and granted it, there must be some substance to the patent, and therefore a defendant claiming invalidity has quite a high hurdle to strike down a granted patent.
Unfortunately, the USPTO takes the view that it's quite costly to examine a patent thoroughly, so do they do a cursory check[1], and grant anyway - they expect the court system to sort out any errors.
So we have each side expecting the other to do the hard work, and neither actually does. The upshot of that is that crap patents are easily granted and difficult to revoke, even when they are absolutely brimming over in bogosity.
The US patent system *has* to change. It is toxic to all - even those that currently profit from it.
Vic.
[1] The USPTO assessment seems to consist of grepping the application for the text "this application is utter bollocks in every respect". If the search fails to find that phrase, the patent is granted[2].
[2] Yes, I had three US patents granted before I knew any better. Yes, they are all total bollocks, and really shouldn't have been given house room. But I didn't *say* they were bollocks at the time...