I work with Freelancer.com, and I presented the concept of bitcoins to the staff the other day.
I also suggested that we accept bitcoins as a form of currency on the site, but unfortunately it was not well received, and with good reason.
Given the amount of fraud that we already battle with daily, I think it is extremely unlikely that Freelancer.com will be accepting bitcoins any time in the near future.
However, once the currency grows and matures I'm sure they could be convinced to take it on in the spirit of competition.