I would rather not wear a bra for two reasons. First, it feels so nice without one. Second, there is considerable statistical evidence that wearing a bra for long periods of time may be related to breast cancer. (In 3rd world countries where wearing a bra is very uncommon, they have a near-zero rate of breast cancer.)
On the other hand, I often DO wear a bra because:
1 - I have 'permanent high-beams' so it's either a bra or pasties!
2 - With 44DD's, if I don't wear a bra, I get sweaty in the crease and that can get stinky after awhile
3 - Any activity that creates bounce gets painful in a hurry
4 - With the right bra, the DD's look GREAT! LOL!