When AJ was buying out Ryan (my former partner) we asked a lot of people about valuation, both adult industry and mainstream web valuation people, and got a lot of different answers.

Revenue-based models, the low end was 6 months revenue, the high end was 2 years revenue, and several people suggested a year if it was relatively stable.

Others suggested a combination of a portion of revenues plus a value for intellectual property (designs, banners, content, etc.)

Our buyout was complicated because we were at the beginning a gigantic growth phase that we had no way to value, so we ultimately came up with a combination of x amount up front and a portion of revenues for a period of time.