Phishing attempts have be lingering around the instant messaging environment for some time. The latest report is from Yahoo, and the exploit is purported to look as though it is coming from a buddy list contact. Upon clicking, the user is redirected to a fake Yahoo page, where Yahoo user information is requested.
You can catch the whole report, including some history of similar reports from other IM carriers, here: Phishing Dips into Yahoo IM.
On a related note, Aconix has some additional insight into the phishing over IM issue. Aconix develops enterprise security products which are designed to protect against such exploits in corporate IM networks. Read more at Akonix Security Center Warns of New Threat for IM Users in Corporate Environments.