A bra (or other support system) is pretty much de rigeur for me these days. Otherwise, I look like a National Geographic cover model.

The top of my very first belly dance costume (which I made myself) came unhooked in the middle of my first public performance (in a mall, no less!). I didn't realize it was unhooked until later. I didn't flash anyone, but I did lose my cleavage and it explained why all the guys were watching me so intently (they were expecting a "wardrobe malfunction" at any moment). Subsequent costumes had industrial grade hooks after that. :-D