One thing that pisses me off about these sites is that there's so many of them. See, reputation is worth a lot, and it's not transferable between sites :( You work hard to gain a high score on, say, vWorker, but then at Odesk you're a fresh dev with 0 experience, unlikely to get any piece of work that can really bring normal pay.
Sure, but when just seeing the "name and rating" of bidders, this detail isn't directly visible. Many times buyers decide very quickly whom to give the work to, based on a very superficial glance on the ratings, without entering each dev page and examining it in detail. This is mostly true for the small jobs.
One thing that pisses me off about these sites is that there's so many of them. See, reputation is worth a lot, and it's not transferable between sites :( You work hard to gain a high score on, say, vWorker, but then at Odesk you're a fresh dev with 0 experience, unlikely to get any piece of work that can really bring normal pay.