Anyone that is trying to ride a horse under 2 years old is stupid, at that age they are hardly more then foals!! (ok, a bit of an overexaduration there but you get the point). My mum's QH Smarty is 7 yrs old, he was broken in by someone when he was a bit over 2. For some breeds (eg. Tb, Arab, ect.) that would be out right stupid, although I still think he was a bit young. The result is a quite, dependable, well educated gelding BUT one with a VERY heavy mouth. Generally he's hanging on your hands although after about 10 mins of work he does come collect.
I don't know if this is because of the age or way he was broken in, but that's just how he is.