Agreed that it's unfortunate that flash can write to your clipboard. The only place I've seen that used legitimately is on bit.ly so they can copy the shortened link to your clipboard. Even there, I usually end up confused about what happened and manually copy it anyway.

As far as things we could do at Facebook, we definitely work to detect wall spamming. We end up blocking this kind of spam a lot the time, but there's always room for improvement.