I still do not have a proper response formulated for things people have forwarded me that I have already seen. In addition to running FilePile, I read blogs. Lots of them. I have over 200 subscriptions that I actively keep track of, so the chances of me seeing photos of Ron Jeremy seeing his first goatse are pretty high.
I don't want to be rude about it, but I just have no simple way of saying, "seen it" without feeling like a jerk every time.