I know I'm gonna take a lot of heat for this...
While I do agree that often people shouldn't disparage someone because of their perceived sexual histories, individuals should be more responsible.
Women in particular have to realize that the "double standard" really is not a double standard. There's a reason why men are "studs" or playas for doing the same thing women do who are "sluts." The salesman who convinces larger numbers of customers to buy from him is a sales wiz because it shows he's got the skills necessary to win over the customers. But the customer who allows ANY salesman to sell him any product, cannot be considered a sales wiz. He may be gullible, or a pushover -- the "ho" in the transaction, but he's not the sales wiz. The salesman is.
In the dating world, for whatever reason, the process really is analogous to the salesman-customer dynamic. Even though in my view the woman is getting just as much out of sex as the man is (at least they are if I'm the man ), it really is the man who has to lay out the charm, and all the other things that will win over the woman. A woman can turn off a man just like a man can turn off a woman, but for the most part, it's the man who's got most of the "convincing" duties.
Therefore, having a lot of sex partners is evidence that the man is skilled at convincing them. People who would give him props do so because they figure he's got that "certain something" that convinces women to sleep with him. On the other hand, since the woman doesn't have to go through the same effort, she can't be a "playa" or a "stud" if she sleeps with a lot of men. All the average woman has to do to get sex is to let a man know she wants him. So if she sleeps with a lot of men, she's like the easy customer in the above example. That's why she's looked at differently. That's why this really isn't a "double standard;" the comparison really isn't apple-to-apples.