http://www.nfl.com/news/story/0ap200...l-sanders-deal

While shopping the Chiefs offer to the Bucs, Weinberg never explained that he had already accepted the terms of Kansas City's offer. Later in the night, Sanders' agent had agreed to terms with the Broncos, which is where he is currently headed. Sanders and Weinberg also rankled the 49ers by agreeing to visit, then blowing it off.
Actually, given the players age and the fact that someone other than themselves is doing the negotiating, I am stunned this kind of thing doesn't happen more often. Unlike the diverted money deal he was sanctioned for, its hard for teams to stop.