Scams on MSN/other instant messanging services

Every so often, I will get some messages from my friends while I'm offline, itll say something like "Think you can beat me? Try to now!" and be followed by a link, getting your attention for you to try and click on it. Today I got two of those, from different friends, being from a site called dekamobile.com trying to sell acai berry crap. My friends don't know that it's coming from their accounts until I tell them, and I've had it happen to me once before as well. I changed my account after that.

Has anyone else had this happen to them?