The Plymouth Whalers acquired Robbie Czarnik's rights from the Oshawa Generals, and Czarnik has left Michigan to play for Plymouth. At least it's a short drive across town for him.
Czarnik had a fairly average freshman season with Michigan, but looked like he was starting to reach his enormous potential this year with 3 goals and 3 assists in 6 games.
More damaging for Michigan is that I've now heard from a couple of different sources that 2010 goaltending recruit Jack Campbell never signed a letter of intent with Michigan during the early signing period. I haven't heard anything official about a de-commit or making an agreement with Windsor of the OHL, and the Big Ten does have stricter rules about the early signing period, but you'd have to imagine getting Campbell in the fold would have been priority 1A for Michgan.
Update: Here is Michigan press release on their early signers, with no mention of Campbell.
Update II: It's looking like Campbell will end up signing with the Windsor Spitfires of the OHL at some point, probably once he is done at the NTDP.