If you cache profile blocks, it will show blocks from someone else's profile. If you cache the view photo block on the iview photo page, it shows someone else's photo, same with videos. There's a lot more blocks that do the same thing. You can't even cache the action blocks on profiles, it displays the subscription form within the block. If you cache comments on the view photo page, it shows your webcam, on and on....
So why does it not cache the block specifically for that page?