Wow, the gender divide is really interesting on this thread. Pretty fascinating. I haven't read the whole thread yet, so I don't know if this has been posted. But here's a slightly-not-on-topic point I would like to make.
Masturbating to pictures of people can create an attachment to those people. This is not much of a problem with porn (since the women are basically pictures there), but can be an issue when you know and interact with those women. Since you know them as 3-d people, the more you think and fantasize about them, the more you fall for them. I'm not saying you have to prevent yourself from fantasizing about anybody when you're in a relationship, but you should be careful not to get yourself too tempted... It's not healthy for your relationship, and it's not really about how great the other person is but rather how much you allow yourself to build them up in your head.
I remember a post in the past from Ratbastid (the truth, he speaks) where he said that to stop feeling attached to an ex-gf, he stopped fantasizing about her when masturbating, and that helped a lot. Something about bonding chemicals being released when orgasming.
Again, nothing wrong with fantasizing or masturbating, but it's good to be careful about unnecessary attachments. That goes for friends, friends of the GF, co-workers etc... Everything in moderation!
