[wand3r]

While I agree that those companies and many others have become quite successful taking this tact, it was really only successful because of those businesses are nearly monopolies. Obviously this is similar to ISPs. Upwork competes with tons of other boards directly as well as LinkedIn, Indeed/Job Boards, Craigslist, general networking and other preferences (not working an additional part time job).

Also, similar to recruiting these places need to attract top talent consistently not just warm-bodies. Highly skilled workers can afford to exercise other options much better.

[shimon]

You're right, but upwork is the dominant marketplace for low-cost contract labor. It is the merger of what was previously a duopoly in the space (elance and odesk) and the network effects are strong.

So maybe it's not quite as monopolistic as the others you mentioned but it has clearly (and rationally) chosen to compromise fairness to its users to a degree that it likely could not in a more competitive market.