Akons fans know the content of his music and most likely are familiar with his onstage antics. Anyone at that show went knowing what they were in for.
The young lady is at fault for placing herself "voluntarily" in a very adult situation, in very adult attire. Akon had no way of knowing her age. That does not excuse his obvious lack of class and lack of talent.
Off Topic Rant:
This is a touchy subject for me because I was always criticized for dressing slutty or provacative when I was younger...well actaully still to this day. When in fact, I was wearing the same clothes as my peers but I had a more womanly figure. I still get stares when I wear tank tops, like everyone else in the world, but I am busty. I've had people tell me I was "asking" for the wrong kind of attention. Hmm...I guess my hips and my breasts are begging to be raped. Soooo...my point is all Women are at risk for rape. In this case her clothing was FAR from appropriate, but clothing should never be a scapegoat for sexual assualt of any type.