Re: "You have to wear a belt"
It's seems reasonably clear to me that none of you have hurt your back. The reality of the matter is, as Dale says, that a properly trained and conditioned athlete--one with strong abs they are able tense properly during lifts which need that to prevent the lumbar spine from getting our of place--don't really need belts. I've deadlifted 465 without one, and pressed 210.
However, if I have one, I ALWAYS use it when I get within 10% or so of my one rep max. When you get that close, you will quite often get very minor form deviations, that can lead to injury.
People will say "don't do the lift if you're going to have a form deviation". This is lousy psychology, and likely comes from people whose "one rep max" is 10% or more less than what they likely could do, even without a belt. The fact of the matter is that you don't get max poundage unless you've committed yourself 100% to that lift. No failure, no retreat, no possibility of anything but success. And on the deadlift, for me, that often means a split second of form deviation. I have a very strong back, and have not hurt myself in probably 6 years--doing countless deadlifts--but I do NOT want to do it again, and belts are not harmful, and potentially preventative of injury.
Obviously, you don't need them in the WOD's, although when I used to straight set the deadlifts on Diane I would wear one sometimes since my back got tired on the third set. Generally, though, your wind will give out first.
Bottom line: you don't NEED a belt, but using one is not a bad idea when injury is possible, at limit ranges.