[Gaia]

I think there is a big difference between dating, and being in a relationship. To me, dating is what happens before you make it official, and why shouldn't you date multiple people at once? It gives you a better chance of finding the person you want to be in a relationship with.
Until you have that conversation to make it official, I think it is perfectly acceptable to 'play the field'
However, I will say that it's not an enjoyable experience having to tell one person that you don't want to see them because you met someone else more compatible.
As for your question regarding the double standards, I've had both sides. My closest girl friends, and guy friends tell me it's perfectly acceptable for me to play the field if I choose to, but I have some other friends who do look down on me, and view what I'm doing as deceitful. Though I think that is because they have more traditional views than I do. As in, they view dating someone meaning they are instantly exclusive, whereas I don't because nothing has been said to make it that way. I have seen the same for men as well, sometimes they will be 'studs' sometimes, 'players'. I think it depends on the people really.
I don't think there needs to be a conversation about the possibility of dating other people. Unless something is made official, personally, I would assume they are dating others, as I probably would be also If the girl gets mad about it, she should have had a conversation with you regarding dating other people. It should not be implied that once dating starts everyone is exclusive.
Of course, there will be many who disagree with me, and that's all fine and well, but that's my opinion on the matter.
So go forth and date, you stud