Now here's the twist. Let's say that your inline ad isn't pulling many clicks. MSN will decide it isn't that relevant, so it gets demoted to sidebar status -- and someone in the sidebar area gets promoted.
I noticed earlier this week I couldn't even get to MSN Search UK at all -- so watch for construction. It's essentially the testing ground for what MSN wants to do in the US and elsewhere, so there will probably be glitches along the way.