Useless idea. You need to invite to make your .NET passport account compatible with Live Messenger 8.0, without it, you can't sign in. I've got it and tested it myself, i can only sign in with the email that i registered the invite with, nothing else.
Wasn't MSN 8.0 made public ? Or did I just get an update for my Beta ? If not, I got some invites also ! ^_^ PM me if UsuckAlot runs out of invites