Chiropractors are concerned that women’s purses may be too heavy for their shoulders, but man bags may come with their own risks:

Recent research shows a guy with a murse is more likely to be mugged, leading insurance carriers to wonder whether they should up their premiums for those men with the latest Gucci tote.
The official reason?
Women can carry huge handbags for fashion, with nothing significant in them (example: my Marc by Marc hobo has a Louis Vuitton pochette, some lip gloss, and a Teen Vogue – hardly heavy lifting).
Meanwhile, guys usually just carry big bags when they need to transport something – a laptop, a camera, a portfolio, or something else of value. Thieves see the big bags, think they’re loaded with the latest iBook, and strike.
But we have our own theory…
Muggers who see man bags may assume any guy who carries one is too concerned with their appearance to fight back and risk a black eye or broken arm, and so they calmly give up their stuff – and keep their cute face and unruffled hair.