I just read this and found it interesting!
According to a study done in a university in Tokyo: bras shape breasts, yes, but there are ligaments inside breasts the main puspose of which is to support them, and external support weakens them so they are no longer able to do so. So in other words, it's very possible that they sag MORE if you wear a bra.
See here:
http://www.susunweed.com/An_Article_Bra-disease.htm
and
http://www.breastnotes.com/aware/awa... Read More