I'm sure fraud & waste exists in all mediums of advertising

$7 billion over meany years, while it seems like a lot, is still just a small amount of the total advertising online market

The figure may still be exaggerated and more research is needed. It could include things that are mistankingly called 'fraud' but instead if a misunderstanding of terminology

In a free market, online advertising fraud would depress prices as advertisers pay less due to worse results. If advertisers were getting 100% human traffic, rates would go up, making the ads more expensive.

So in the long-run it balances out. But on an individual level it sucks getting scammed.