Today is the first time I got 25 hits that were empty when I searched for "Feynman" though. Something is odd with the search algorythm...
I suspect part of what's going on has to do with the aggressive retiring (deletion) of old threads on a number of boards. That's done via a back-end script I wrote, which doesn't engage the forum software directly, just the database -- so it doesn't necessarily do it in the cleanest fashion. This may result in search keywords that point to posts that no longer exist, still sitting there in the database turning up hits when you go searching.
I try to do a maintenance run in the software every now and then to clear out broken/confused bits like that, but there's always some hang-time during which you can run searches that get results pointing to nowhere.
A theory, at least.