Not sure this is a real thing, but...
First and foremost, when I go braless, I have the gravity of a thousand suns trying to ruin my life. So, Imma wear mine, thx.
Second, any day should be go without a bra day. Not my boobs, you do what you want with yours. I agree that it can be inappropriate (but that's about people being Puritans). By declaring a day "Go Without A Bra" Day, we are implying you are not allowed to do this otherwise. Maybe we can also have a "Wear Your Hair In a Ponytail" Day and a "No Panty-Hose At Work" Day. You know, so we have the freedom to not style our hair and to show our sinful, sinful legs.
Third, and this is because of The Big Bad Patriarchy, this is just going to result in heartache for us. It will be re-named, "She was asking for it, did you see what she was(n't) wearing?" Day. It will be named "Get Sexually Harassed More Than Usual" Day. It will be name, "I always thought that girl was a dirty slut deep down, and now I know it!" Day.
Fourth, breast cancer has not directly touched my life but I don't see this as particularly supportive (SEE WHAT I DID THERE, DO YOU LIKE ME YET). Are we letting them out to bounce around in solidarity (because I don't think that's very solid..ari...tous)? I don't think a Fuck You to bras is really helping anyone, or even conceptually sound. A Fuck You to bras is a Fuck You to patriarchal reasons we wear bras (not including gravitational reasons!), not to breast cancer.
Fifth, by the same token, it would seem that flashing my boobs around town would MORESO help support breast cancer research. "See these here breasts that I have? If you'd like me to keep them, please donate money." Even then, not so sure about it. It seems insensitive.
There are Six Things I want so say.
I suppose this can be viewed as celebrating breasts in support of breast cancer research, which I can get behind a little. "Ok, we like breasts, let's show how much we like them so we know how much we hate cancer."
I dunno, this just screamed, "LOOK LADIEZ, IT'S OK NOT TO WEAR YOUR BRA ON THIS ONE DAY! IT'S FOR CANCER, SO IT'S OK!" to me.