Too many, I think, depends on age. If someone is 17, 12 sexual partners is probably too many. If someone is in their mid-30's, that sounds reasonable. Let's hop into the wayback machine.......
They are in junior high. They don't have sex with anyone but maybe fool around a little. So far so good.
They are in highschool. They have a different bf/gf every couple weeks it seems, but they don't sleep with all of them. Some of these relationships click for a while, and they sleep with two or three over the course of their highschool term.
They are in college, and also maybe working a part-time job. This would probably be when you would have the most 'occurences,' as many people go wild in their college years. The numbers here could be anywhere from just a few if they are only in college to study, or in the triple digits if they are a wild sorority chick, and have to hook up with an entire fraternity. I would say 4 or 5, on average, is not unreasonable in these years. Figure a few were real relationships with maturing young adults, and a few were just one night stands or quickies in the dorm, just for the hell of it.
Post-college, they are out in the 'real world' and the dating scene that comes with it. Either they found the love of their life in college, or they are out partying, or they are still out searching for that special someone. Again, the numbers could range from very low if they are pretty conservative, to triple digits if they date a different person every weekend (and hook up with them). Gonna go ahead and say that '10' throughout your whole mid to late twenties is not a far stretch.
Thirties. If you are not looking to have children and you are a woman, this time period is probably fun because your sexual 'peak' is still going up, and you are very comfortable with your body, you know what you like. You may be a cougar preying on younger men, or you might like older men, who knows. If you are a man and still in the dating scene, you've probably got your game down (if you had game to begin with), and you get some where you can. If marriage isn't on your list of priorities, you could theoretically continue this until your viagra years, assuming you kept your body up. If you are a woman still looking to get married and have kids, this is when that whole 'biological clock' thing comes into play, and you may up the 'numbers' in an attempt to hook a guy and start a family. For someone in their thirties not currently married or in a serious relationship, I wouldn't say '15' was too much, because afterall you are a fully grown adult, and you are probably less likely to form an emotional connection with a new sex partner, as opposed to if you were still in your teens.
A lot depends on how conservative or open you are when it comes to sex. As far as the OP question, for that age, I would say 12 is erring on the side of too much. I mean,
really, could they all have been wholesome, emotionally connected relationships? In that span of time? Now if you were in your late twenties, that doesn't seem like too much. One per year seems well within reason.
I would never personally ask someone how many sex partners they have had.
1. Nobody ever tells the truth. I know,
some people do. But honestly,
nobody really does. Selective memory plays a part. So does alcohol.
2. It's insulting and judgmental in a way. It really would be like asking for a persons credit report. Why? You don't trust me?
3. You can figure out everything you want to know about a person's past by simply getting to know them. Their body language, confidence, allusions to previous partners, attitudes toward sex with you, expertise in bed, hell even the clothes they wear, can give you a lot of info that you don't and shouldn't ask for.
4. STD's can be tested for. Even one occurence of sex in their past, even WITH a condom, and they might have an STD. I know some of you have this idea that a condom turns a penis into a magic wand of safety, but that's just not the case. Condoms do not cover areas around the base of the shaft, nor do they cover any of the *******. When things get heavy and wet, viruses can travel around the rim of the condom through fluid (not semen) and become a lifelong sex partner which you cannot get rid of. Testing, solves all of this. Are we infected? Nope, no problem. Yes? Ok it's not the end of the world, we'll deal with it. Asking about sex partners doesn't change a thing, you still must get tested.
5. Nobody, I think, has ever flat out said "Well, I've probably been with about 200 to 215 people, I don't remember some of them." You will never hear this, what you will hear is a smaller number like "Three," or maybe even "Six." Or they will dodge the question completely, for example "I've only had three boyfriends." If someone looks skittish about my history when they ask me this, why would I say something that might possibly disturb them? Even if I wanted Full Disclusure in our relationship, I would have to take into account the fact that I want the relationship in the first place, and TMI might break the deal. Better to gloss over certain things.
6. By the time I come to the understanding that I'm starting to fall in love, I have either: A) Figured out how many guys she's been with through my clever sleuthing ability, and decided it doesn't bother me enough to affect my feelings for her. Or.. B) Figured out how many guys she's been with through my clever sleuthing ability, and realized that it's just too much for me to deal with, and instead of wasting her time and mine, I'm just going to break it off and we'll be good friends.
The only reason I would be uncomfortable with a woman who had a significant amount of sex partners in the past (we're talking a lot) is because I question her self-control and character. It would be similar to finding out that she had a gambling problem, and lost 300,000 at the casino in one night. What..?? Why on earth couldn't you control yourself? Or overindulgence in alcohol. Or any number of other character traits that might make me stop and wonder if this was somebody I wanted to spend all my life with.
Always remember: The mailman comes around six days a week, is she the type who can keep it in her pants when I'm not there? Even if he's a tanned, chiseled adonis of a mailman with a 10 inch weiner? She's a keeper.