I'm working on an SEO app that (among other things) shows the number of incoming links to your site over time.
There are a few ways to get this data. Scraping Google "link:yoursite.com" results gives you some (not all) of the links they know about, but they aren't too happy if you are doing lots of scraping. Similarly Yahoo has their site explorer API calls which give you 20,000 queries per day I think, but it has a non commercial use limitation.
Are there any services out there which provide this information in some kind of API call? Probably a pay service would be best, need something reliable for commercial use. Basically it would have to be an index of the web that was updated fairly regularly selling API access to it. Or any other ways people get this info short of writing a SETI at home type app to make a bot army of scrapers?