I saw this in an article the other week and I thought it wasn't a bad idea.
It fills our projected need in the 2011 draft, which is probably a RB if Jacobs continues to decline or not stay healthy. Marshawn Lynch is a beast of runner who can move a pile with purely his amazing strength and VERY good yards after contact.
If during september-october lynch plays poorly, we can get him before the trade deadline (while his value is at his lowest) for a 3rd round pick and give him a fresh start? There are a lot of hypotheticals in this trade but I don't think it's honestly a half-bad idea.