No, JiveTalk doesn't create spam...the spam I am getting is from YIM. I don't use the Yahoo client because it was extremely unreliable for me and I had to manually restart it several times per day. JiveTalk allows spam messages through so I end up getting more spam than real messages. Since there seems to be no feature to allow ONLY messages from those on my buddy list, I stopped using it. It is very possible I would be getting the same spam through YIM, but I don't recall that happening when I used it. I don't blame the spam on JiveTalk, just the inability to stop it from coming through on my phone. If you don't get spam now it's probably safe to use JiveTalk.
BES 4.1.6 Exchange 2003 SP2