I believe there are various medical reasons for alcohol to effect people differently (one of which is body weight, which presumably is a part of it for me), but also it's very influenced by experience. The more you drink, the better you can hold your drink.

I think that's probably the reason for your link between people with high tolerance and people for whom alcohol became a problem. It's not that having a high tolerance is problematic, it's just that anyone who gets drunk enough to have problems with it has probably drunk enough in the past to have built up a pretty good tolerance.

Personally I find my tolerance level varies greatly - I assume things like tiredness, what I've eaten, time between drinks and other stuff is in play, but I've never really clocked the exact causes. For example when I'm at Arsenal games I'll always have a couple of glasses of wine at half time, and usually feel a bit buzzed from them - drinking the same while in a restaurant, or at home, wouldn't do anything. Presumably there's a pattern of my behaviour before/during these games that makes it happen.