A guy was downloading porn at home in his room with eDonkey, when suddenly he hears his dad yelling from the next room "hey! what are you downloading in there!". So he wonders how could his dad possibly know what he was downloading. In the discussion that followed it turned out that daddy also had eDonkey open on his computer and happened to be sharing the exact file that his son was downloading, realizing this when seeing a familiar IP in the downloaders list.
This must be true because it was said on IRC (#bf). Reported on ircquotes.net (similar to bash.org).