On multiple Windows Live Messenger accounts (formally MSN Messenger), we received the messages (don't visit the link!):
Get surprise at hxxp://www.messengerweb.info/ Unbelievable!
Hey, hxxp://www.messengerweb.info/ helps u find out who is your friend!
U have deleted me! Look here hxxp://www.messengerweb.info
Was this a new worm? Or a bot that was sending out IM spam? Turns out it is neither and instead much more like adware. The site being advertised states they can find out who may have removed you from their contact list. All the service requires is for you to "enter your MSN account and password and we will tell you who has left you out from their lives."
However, if you read the fine print, it states "By using this service the user allows Messenger-Tips to send intant messanges [sic] to your online contacts and/or change temporarily the nickname in order to advertise free this service."
Symantec Security Response Blog