PhotoGregg, I totally see what you are referring to ... the point i was trying to make is that demographics is probably the wrong word in this industry, or that our demographics are not the same as mainstream ... like mutt said, it doesn't help you to know the age or annual income or location of house - you just want them either a) at your site or

somewhere else ... the somewhere else is where the market research comes in but it already exists in almost every company who directs traffic ...
Personally, I have a great interest in the demographics of my members - especially on my womens sites. But, i'm also at an advantage. Women will complete a form for prizes before returning to the erotic features ... men are there to wank and could give a shit about getting a cd/prize for filling in a form. I have gathered a lot of demographic data over the 4 years of purve ... here's what i discovered ...
1) some women buy porn, some don't
2) some straight men buy women's porn
3) some gay men buy women's porn
4) some older women buy porn
5) some younger women buy porn
6) most women can be found surfing mainstream sites such as astrology, sexual education, etc (ie, this is the only important & effective piece of demographic information i have gathered in 4 years of constant surveys & data collection)
At the end of all of this research, what i have learned is that the most successful marketing is those who market into mainstream and bring those women into adult.
All the other bits of information do nothing to assist my marketing efforts and they don't make me any more money ... I only do thus because I intend to market women's products into mainstream eventually.
So, I guess it all depends on your business plan ... but the cart has to come before the horse (ie, the traffic before the demographic data)