there are two reasons why I always thought Michigan had some kind of realistic shot with Hall, and those are;
1) His perception of the Depth Charts. Michigan actually took more OL in the 2008 class then Ohio State did, however, the Michigan OL class wasn't as widely recognized or nearly as highly regarded as the Ohio State OL class was. I don't think Hall is scared of competition, not what I am suggesting at all, but the only really "big name" recruit that Michigan signed at OL was Dann O'Neill, whereas Ohio State signed Mike Adams, JB Shugarts, and Mike Brewster. Ohio State also got a transfer of a highly regarded OL in Justin Boren, which means if Hall were to redshirt in '09, as a RS FR in '10 he'd have to compete with a RS Soph. Justin Boren for a possible OL position at one of the guard spots.
2) Playing Time. I think at Michigan he might be able to play as a true freshman. Not necessarily start, but he would most likely play early. Did you see our OL in 2008? Almost all of the OL that we took in our 2008 recruiting class needed to put on weight and add strength, which is why none of them played despite having awful upperclassmen start like Tim McAvoy and Dave Moosman. That probably won't be the case for Marcus Hall. Hall already looks like a man at only 18 years old, and my guess is he could probably start at RG for Michigan from day one.
I still think ultimately he winds up at Ohio State, but those two primary reasons are why I always thought Michigan would have a shot. Him declaring Michigan as his leader right before he's set to go on officials to Miami and Tennessee actually probably helps Ohio State. Instead of those Southern schools trashing Ohio State to him, they are going to be trashing Michigan to him.