Sheff. Utd fan at work asked me a similar question re: SAFC 'hoolies' not really being in the public domain.
He's been to Sunderland a few times and said he's never had any bother but sort of knew to keep his mouth shut, have a quiet pint, a bit of friendly banter and it'd be OK. Like at the majority of away matches.
Considering the turn out we get at away matches, and the number of people who are a bit 'handy' (I'm excluding the gobby chavs, talking about genuine hard-cases), then ther's the potential for a very large very nasty mob.
But like someone mentioned, the vast majority of our fans want a laugh, a drink, and to watch the footy. And we think that those who go out of their way to have a bit of organised pagger are a bit dim.