Most FPS issues seem to come from powerful PC's bottlenecked by inferior graphics cards (as usual). Still these days (2010) people don't really have that much understanding of what is in their PC.
And I think it's more prominently here because adventures in general aren't as demanding as, say, RTS and FPS, whose gamers need to pay attention to that at all times to run their games (*sigh*).
I mean; you got a Quad-Core, 4+GB memory and run a GeForceFX8xxx or older? Seriously?
(Okay, well, I could see it if it was a 8800GTS, but otherwise...)