Bannister is a great ST player and very hard worker.
He reportedly has worked hard at learning to play WR, which he wanted to do after feeling like he was getting pigeon-holed in a ST role early in his career. he continued to perform on ST, but when he re-signed with Seattle in FA it was with the understanding he would get a shot at playing some WR as well. He is a tall WR, at 6'5", 205#, and must have some athleticism to be such a good ST player.
However, he broke his collarbone in the middle of the 2004 season, broke it again in minicamp the following offseason, and then re-injured it for the final time last September. I would think he has had enough time to heal, but the possibility that the injury could occur again is high enough that Seattle decided to cut him.
I wouldn't mind the Pats taking a flyer on the guy, but whoever signs him likely won't offer him more than the minimum. He is also likely to be asked to sign a split contract, which means he only collects half his salary if he ends up on IR again.
Keep in mind, Bannister was born in Ohio and went to college at Eastern Kentucky. Though he has played for Seattle his entire career (they drafted him), it wouldn't surprise me if he ended up with a team in the Midwest somewhere, like Cleveland or Tennessee.