From what I've seen, the whole debate over what age to break a horse varies greatly from western and english. A lot of western folks break their horses at 2 and have them ready for futurities, it's a business. English people seem to wait longer to back their horses.

For me, three is about the right age. I wouldn't turn down a horse that was backed at two though. Just because it was backed at two doesn't mean it will have soundness problems, though it is more likely.