I still remember the time I had a presentation with some content that I thought was funny, but just to make sure, I asked several female friends, all of whom thought it was OK. I still received some rather negative feedback from women I had never heard of. Surprise! It turns out that the people I know are, well, people that I know and we're more likely to understand where one is coming from.
What I, and all of my female friends, missed, was the issue of context. Just because there's a joke I can tell in front of my friends doesn't mean that it's appropriate for for a large, anonymous audience. They don't know who I am, they don't know what I think, and it's quite reasonable that someone may be offended by a "let's judge Demi Moore by the size of her breasts" cartoon.
I honestly don't understand why more people don't get this idea: public and private behavior are not the same and should not be the same. I have a friend in the UK who greets me by saying "hiya c*nt". There's a private joke behind that, but he would never dream of greeting me like that in front of a bunch of people he doesn't know because it's not appropriate.