So I tried a few years ago. Was looking for an old obscure TV show and couldn't find that anywhere. Installed aMule on a whim, got it connected and used the search function. Actually found the show, started the download. A minute in it found a couple peers and started downloading, very slowly. Then I remembered that you can see the file name that all the other peers stored the file as locally. It was handy back in the day (around 2001) to spot fakes. For some reason, people back then liked to rename random movies or porn to current blockbusters, so when you look for a new movie you get the wrong thing. That's why eventually websites that manually indexed links took over.

So I opened up the window that shows all the file names of the tv show I just added to the download queue, and most of them very explicitly hinted at child porn. I freaked the hell out and nuked the whole installation, deleted everything, overwrote empty parts of the disk with zeros. It just downloaded a few kilobytes of a couple hundred MB, but still... I just thought what would have happened if I hadn't remembered that file name thing and would have found out when trying to play the damn file after downloading it. So probably not gonna use it again anytime soon.