Google, as the most dominant search engine, has the power to kill most on-line businesses - and they have used this power before - so, when you think about doing something Google doesn't like you have to think about the risk on getting caught and see if you can tolerate that risk.
With an ad network the risk of getting caught is very high, there is standard code you have to add to your page to show the ads and it's trivial for Google to detect it.
So, it's just a matter of time until Google decides to penalize this network and when they do you will go down with the network - not a good deal in my opinion.
I myself would never do something Google doesn't like because I'll probably take a serious financial hit if Google penalizes my site.