My friend Julie recently started seeing a guy more seriously and they started to talk about their respective sexual history. My friend divulged what she thought was appropriate: serious relationships, a few tidbits of her single escapades, and a break-up or two. And then he asked the quintessential sexual past question: How many people have you slept with?
She thought little of it, shared the information, and then recanted the same question back to him. Suffice it to say that his answer surprised her. His number was four times Julie's (double-digit) number. She told me that she had to hold back her grimace. Because someone with that high of a number couldn't possibly be relationship material (OR CLEAN!) right?
Personally, I never ask the question. It's a mixture of just not wanting to know and it not being really important to the equation of whether or not I am going to like them. Is the number of sexual partners your SO had important to you? Would you not be with someone if they had a high (or low) number?