well I think windows live messenger profiles are pretty accurate. One of my contacts had deleted me this summer (not blocked) and it was showing up on his profile: You have invited xxxxxx in messenger.
A few days ago I opened a conversation with him and weird, on his profile I read: "You are friends with xxxxxx in messenger etc"
Also, I've noticed that when you delete someone (even without blocking him/her manually) that person is blocked by messenger automatically. I've tried several times and when I add the contact back the contact appears on my list as blocked while I NEVER blocked him myself. And I'm using WLM 2009 by the way.
Actually you could conclude that all your online contacts haven't deleted you for sure