The collaborator for the main site used to work @ cap, and we've been evolving a REST API to simplify calling into mturk.

For quality, we don't use arbitrary mturkers. Getting good results on mturk takes a lot of experimentation: I now think about it is as a combination of HR agency, traffic conductor, and street vendor. The challenges of building a useful & sustainable app on it are a bit different from what's addressed by crowdsourcing research papers, though that's not so surprising in retrospect.

Sounds like this deserves a blogpost. It's been a fun summer project. Basically, nodejs with roll-our-own crowdsourcing algorithms, APIs, and UI widgets. A lot more to do, but it's finally good enough to address my proofreading needs, and I'd like to help others who also need to get some writing done asap :)

Btw, we're $0.004 / word, not $0.04 ;-) That means we already cost 60% less than shops with comparable quality and slower turnarounds.