Check out that link. It's decidedly anti-bra, but does give some good points for not wearing a bra. I like how they disprove the famous myth that bras prevent sagging. Bras give support, but genetics determine the size, shape and sagginess of them.
I personally love my bras, but I have gone out in public without one. I'll usually put on a wife beater (or men's A shirt if you're PC) under whatever shirt I'm wearing. I also use wife beaters for regular layering. When I'm sitting around my house and know I'm not going out again, I love being bra-free. I don't sleep in bras, either, unless I fall asleep during the day.
I know some women feel more comfortable wearing a bra most of the time. Some women by "leisure" or "sleeping" bras to wear at night. These are less supportive than everyday bras, but still offer some support and comfort.
Of course, we know there are women who never wear bras. This is usually paired with "hippies", but is seen in all genres of women. A lot of people refer to a study that was done (referenced in the above link) that seems to conclude that bras cause breast cancer. Ha!
First, the study was done for women who wear bras 24/7. I've never met anyone that wears a bra for 24 hours. Did they just not count showers and sex?
Second, there is no mention at all of a proper fit. The study reports that bras compress the breast area, and this causes much higher breast cancer risk. Another reason I do like the above link is that they point out that a properly fitted bra might not cause this pressure and compression.
So that's it? That's all they got? The same site, different page, told of a British study on breast pain. They took 100 women with breast pain and told them not to wear a bra for 3 months. The pain went away. Upon wearing bras again, the pain returned. Again, absolutely no mention of whether or not the bras were properly fitted. If you read my first post, I experienced breast pain whenever I removed my bra, and general discomfort while wearing it. However, that pain and discomfort went away when I started wearing bras that actually fit me.
So, am I for or against wearing bras? Neither. I am more comfortable wearing a bra in public, but I admit that it is mostly to do with society and how others view me. I know that my larger breasts get pretty sweaty when it's hot, and wearing a bra prevents chafing on my sweaty boobs. I know that wearing a sports bra is the only way I will ever exercise, because bouncing around hurts them. My husband will attest that I hold them in place if I have to run or walk fast when not wearing a bra. But, some women are OK with the bounce factor.
Basically, it's all up to you in the end. If you choose not to wear a bra because bras hurt you, you should try getting fitted before ruling them out completely. If you think bras will prevent your boobs from getting saggy, you are delusional - time and genetics will win.
One final thought in the decision of whether or not to wear a bra: Fashion. If you like fashion, remember that quite a bit of today's fashion is designed around the societal ideal of a perky breast. I have clothes that would never look right on me without a bra. Some wouldn't really fit without a bra holding the girls in a "perkier" place. It's just a thought.
And yes, I'm a fence sitter on many other issues as well.