For translations from non-Latin scripts to English, I've seen people put up PNGs on Mechanical Turk, which seems hard to game--- OCR is usually bad for non-Latin languages, and people who don't know the script usually can't even retype it well enough to put it into Google Translate. Might not work well for alphabets that are easy to learn (Greek, Cyrillic), but if you put up a PNG of Arabic, you probably aren't going to get many non-Arabic-speakers who can do anything with it.
Many translation services don't qualify their translators, often accepting them after a CV submission. At myGengo we qualify them through tests, and maintain quality control through regular spot-checks. We're based in Tokyo atm, so we're pretty good at Asian ⇄ European language pairs. You can check out an unsolicited 3rd-party review by a translator here: http://drane.it/2010/01/mygengo-fills-a-niche-and-does-what-...
No, it's different. In second life you meet with and talk with someone. You do a little mini-interview, and then typically you test one sample of his work (I have a native speaker friend for each of my languages).
Then he does the work, we proof read it, then pay.
mturk you put it out, people translate it (mostly machine), then you have to reject it, put it again, same thing happens. Etc. Quite different beasts.
You may want to try CrowdFlower (disclaimer: I'm on the engineering team), which is a Dolores Labs project that connects users to several different crowdsourcing marketplaces, including Mechanical Turk. We offer a GUI for designing tasks and backend algorithms that automatically reject untrusted work.
