I'm finding some clues here. To see what I'm coming up with, check this links
http://www.apostropher.com/blog/archives/002436.html
This blogger actually openly claims to have posted the tubgirl and goatse images here. The date is April 15, so it's not this incident, but could be related.
That would be the vandalisation of the FReeper Canteen thread.
If you are not familiar with 'hot-linking', just think of it as though a person were powering all the appliances in their home via an extension cord secretly plugged into a socket at your home. That person is getting all the benefit with none of the cost while you are getting all the cost with none of the benefit.
Hot-linking is a real problem ... (I know because, as a result of people hot-linking images from my pages, I once was billed over $11,000.00 for one months bandwidth in excess of quota!!) ... and replacing images that are being hot-linked with really nasty ones is a very common method of discouraging such practices. I've done it myself a few times....although not with anything as raw as those images.
No, this is what he says:
it was fun replacing the unflattering images of Nancy Pelosi and John Kerry they were hotlinking with tubgirl and goatse
It seems that some FReepers were posting pictures of Kerry and Pelosi that were hosted on his website and he swapped the images on his own server because he didn't appreciate the bandwidth drain.
It's naughty but legitimate. I've done it myself (I replaced this image with this one )