I was denied for my Lionbridge application I have a pretty impressive resume and I am not sure what it was that they did not like. I read somewhere that they do not allow people to work for other similar companies at the same time and I listed Mturk and TranscribeMe on my resume as current so I think that's what did me in. I will try again in 6 months and list them as prior employment.
Sorry about quoting such an old post but this is still relevant for me.
I'd have assumed that if Lionbridge had qualms about you currently working for, say, Mturk, they would not have rejected the application outright. The 'don't bother asking about applications' policy is annoying but I do understand where that comes from -- I mean, they must receive thousands of applications regularly. But working for a competitor is experience that should actually be helpful for Lionbridge candidates (at least theoretically). Perhaps they would stress that if you were to take a job with them, you'd have to drop your current 'competitor' job. Then again, perhaps logic is a not a factor here.
I did something similar, but I did mention in my application that I'd be willing to drop Clickworker if I got into a better project.