Where do these tools get their data from, in terms of listing the keywords that advertisers are bidding on? Do they do this via their own propietary spidering/scraping of Google, or is there some other data source available that is less commonly known?
I've always wondered the same thing. From what I can guess most tools scrape the google, overture and other search engines. I wouldn't put it past google to sell or license their more detailed search data.
I'm pretty sure Google wouldn't be able to sell that data - selling advertiser bid info to potential competitors would likely be against their own terms of service. I figured it was scraping, but it seems like a huge amount of keywords to scrape. Would be a huge technical challenge. Also don't know if there are multiple scrapers, or maybe just one or two which license their stuff to others.
I don't know of any API that shows Adwords placement, as far as I'm aware the Google API only shows organic listings? And the Adwords API is for other purposes.