In the long term, this devalues a click. The
very moment things turn...
Why would you expect a sharp turn? Some fraction of clicks on the internet are already fraudulent, and if people start using this product that fraction goes up. But it doesn't really matter because it's all auctioned.
Let's say I run a billing service and I've placed ads on searches for "billing service". I find that it costs me $X of advertising per incoming visitor, Y% of these convert into customers, and a new customer is worth $Z to me. I'm willing to bid up to $X x Y% on ads. Now lets say a lots of people switch from blocking ads to giving them fake clicks and now half the clicks on my ads are from this extension. Y% drops by half, because half the visitors from this source are now just browser-extension bots, so I'm only willing to bid half as much. But so is everyone else, which means my new 1/2 x $X x Y% bid is still competitive, and there's twice as much traffic to bid for, so it all comes out the same.
Ad networks take click-fraud very seriously because it's important to their reputation, but the market is actually pretty robust to it.
(Plus this browser extension sounds like it would be really easy for the ad networks to filter out.)