Focused Crawling
bixolabs.com
bixolabs.com
Maybe I'm missing it, but with the ease of web crawling, and the capabilities of open source data mining tools, I think these guys are serving a VERY small market.
As to your question, we don't use 80legs. We build workflows on top of Hadoop/Cascading/Bixo, and run them in EC2.
As for the size of the market, I agree that just writing a webcrawler isn't that interesting; you can easily use Nutch, Heritrix, or (for small stuff) roll your own, though the ins and outs of large scale webcrawling are definitely non-trivial.
We've found our sweet spot to be customers who use the raw webcrawl results as the starting point for a data processing workflow. Sometimes what happens next is simple (extract particular types of data off pages, turn into XML, push to the next step) and other times it's more complicated, where natural language processing & machine learning are key steps.
You mentioned open source data mining tools - which ones are your favorites? We use a lot of open source, but after my Krugle startup days I know there are always 10 more alternatives to every project that I haven't yet heard about.
Thanks,
-- Ken