It would be distracting, bandwidth eating, and almost impossible to monitor/Moderate. I wouldn't expect to see it. But, if you are Facebook friends there is already chat there.
Just to add to that, it would allow a channel where people upset at losing could get abusive and angry at their opponents who beat them.
FC Bristbury
Season 5, Level 5
League Winners Levels: 1, 2, 3 & 4
Champions League Winners Levels 2 & 3 Double X 2 (League and Champions League), Levels: 2 & 3