Click-Fraud and the Economics of Anonymity

CNET’s fascinating piece today on click-fraud is deservedly getting a great deal of attention. It is a big issue, and it shows every sign of getting bigger.
Where there is a problem there is an opportunity, though, and I’ve been looking at a few companies who are hoping to build anti-click-fraud businesses analogous to anti-spam businesses. And I like the idea, but I’ve yet to see anyone who can explain to me how you get big by selling to ad networks. You make a few system-wide sales, but the number of potential customers is vanishingly small. Is the opportunity better with selling to advertisers themselves? No question — so where are the start-ups?
As a side note, the following quote from the CNET piece is almost too good, but it is fun for what it says about anonymity and people’s willingness to do one another dirt online:

Joe, the chief executive of an Internet marketing company, enjoys clicking on his rivals’ text ads on Google and Yahoo because his competitor must pay as much as $15 each time he does it. Eventually, such phantom clicks can add up and drain a rival’s budget.