Porky Pie

I wear a belt for deads usually, sometimes I forget but it doesn't seem to make much difference - so perhaps its habit now. Some amazing olympic lifters don't wear belts at all. Certainly you shouldn't neglect your core muscles.

For heavy squatting - I think you should wear a belt - less for the back, more for core stablisation. The best squatters are powerlifters and you don't see many not wearing belts in competition.