Yep. I remember reading on Wikipedia about a longterm editor of theirs who had (according to herself, and I believe it, she sounded quite true) happened to share her connection with a close friend who was staying with her for a week. The friend was also a WP contributor but a bit less prominent, and they came to share the same IP number for that week which resulted in accusations of sockpuppeting and abusive talk through that "puppet account". Ultimately the longterm editor was first blocked and then perm banned: she was unable to prove that she and her friend, behind the other account, really were two different people. I don't know in a very precise way but I would think the methods of tracking users here and on WP are kind of similar.