Companies don't really sell for multiples of revenue, but the math is easy so everyone does it.
I've read that Doubleclick sold for 10x their revenue of $300mm.
And that Right Media sold for 12x their annual revenue of $70mm.
Please correct me if I am wrong on these numbers as I am just relaying what I've heard and don't have access to the financials of privately held companies.
I believe that ultimately price needs to be factored as a function of EBITDA - earnings power. It could be the present value of future cash flows, it could be a mutiple of current EBITDA, it could even be a multiple of the cash flow that a buyer believes it can get by merging the asset into its business.
So when I see online advertising assets trading at north of 10x revenues, it makes me think that it's the latter factor at work.
I've heard that AOL monetized their acquistion of Advertising.com buy running all of their unsold inventory through Ad.com and that they got a tremendous return on investment from doing that.
So that may be the play for Yahoo! with the Right Media acquisition. And thus a multiple of current revenue or even cash flow is largely irrrelevant.