[thetrumanshow]

To answer your first question, you should simply benchmark against the average Mechanical Turk worker's ability to classify links. Build a set of tests from the workers and every time you update your algorithm, you'll need to run against the dataset to see if you've improved anything.

For the second question, your product would be most valuable as an aid to contextual advertising (what ads should I display?), and its possible that you could charge per 1K requests. I have a need for this myself, so I would be happy to be a beta-tester.