Using other computers, unwittingly, to store files was long the mainstay of many software pirates. Many would set up FTP servers on many small business and educational servers, because oftentimes the sysadmins barely knew what they were doing. Often a single FTP "site" would actually be spread across many computers, sometimes dozens of them for a single site. But dumping a bunch of files, be it warez, kiddie porn, or whatever, onto a single computer is just lame.
Of course, I've never seen such a thing happen. I just heard about it once at a TPUG meeting. (Somebody'll get that).