I actually submitted this exact idea to YC last year. Here are some competitors: http://translationcreation.com/ (site down at time of writing) http://www.proz.com/

The YC-segment could probably be convinced to use something like this (I'd use it if the editing/checking worked well). I know of several tech-startups that use mturk in a way similar to what you describe.

A big hurdle for wider uptake would be confidentiality of texts to be translated.