It takes a long time for companies and corporations to catch up to the home user. Many companies are just getting into email. It works well behind a firewall and you can tweak the security on it. As for security, I'm getting tired of hearing about how pc's are making security more of an issue. Before the wide spread use of pc's, security was even more of an issue.
Paper is the worst security hole there is.
Don't mind me, I'm just bitching today. I think that corporations would be able secure company wide IM operations relatively easily using the Exchnage 2000 IM feature. We use Post It software notes to pass notes back and forth across the network at work. That way we get to chat and goof off without flooding the company email system. I don't work with alot of confidential informatioin but i can see how it could be a security issue.