...by posting Content on an AIM Product, you grant AOL, its parent, affiliates, subsidiaries, assigns, agents and licensees the irrevocable, perpetual, worldwide right to reproduce, display, perform, distribute, adapt and promote this Content in any medium. You waive any right to privacy. You waive any right to inspect or approve uses of the Content or to be compensated for any such uses.So if AOL decide they wanted to post logs of your AOL AIM/iChat conversations, they could do so at any time.
I have to confess that I've never read Microsoft's service agreement for their IM system. Even if I abandoned it, and ran Jabber on my own server, I have no idea whether the law protects my chat conversations, as it protects my physical mail and telephone calls. I don't even know which law would apply: Ontario? Canada? Something else entirely?