that's really shallow. it doesn't matter what their past is. you shouldn't care about that. unless you know if they were cold blooded killer or something but you know what I mean. just because they've been in lots of relationships doesn't mean they're whores. its all just for experience until they find their mate. and don't listen to the superficials who only care about image either. you shouldn't care what others think. they'll never get you anywhere in life.
It would depend on the age and years of experience most people who are single will cycle through a relationship twice a year anything more then that with in a # or 2 and their more then Likely just useing people. You don't want to be used.
Depends. Moral issue or practical concern? Morally you might feel their behavior is irresponsible, shallow & are that you are just another brief, sexual conquest. Practical side - they just might like sex, a lot. (lol) Can you keep up with them? Or, could they they have children? An STD or HIV? Responsible adults weigh these things & choose partners wisely. Behavior matters.