The following is part of Seth Wickersham's ESPN Blog:

The 49ers didn't get rid of Barlow because of character problems. They like him personally, even though they knew he'd say a few things every year that would make them scratch their heads. They shipped him because they love RB Frank Gore as a starter and Mo Hicks and rookie Michael Robinson as backups. This is a rebuilding team that doesn't need four tailbacks with so many problems on defense. For a fourth-rounder straight up, the Niners were in. (The Niners, by the way, are loading themselves with middle picks for the '07 draft.)