Getting shut down by Google is always a possibility, but I think the chances of that happening are very remote.

Similar keyword tools for search have been operating at scale for years without any trouble.

I think the reason Google puts up with this is that they know that it's very hard for new advertisers to build successful PPC campaigns.

And, ultimately, the end result of people using our software is that they will build larger campaigns that run longer and end up spending more money on Google.

Yeah I use pretty much the same logic for my business, pretty much all through the API although we might have to scrape ad sense down the track, the stats reporting side at least depending on if the api is easier to use now or not.

Google can be counterintuitive with ad related stuff though, went to a great deal of trouble to support OAuth with adwords but as of yet are still missing report downloads which pretty much makes it useless for the vast majority of applications.

I guess when it's business against business, spending more money because of it is always a win for Google. They have shown more and more of late though they are prepared to put user experience before profit by banning low quality ads. I guess in terms of business against business it would take some major advertisers to oppose it before they went down the same kind of path.