I really hope oDesk - Elance won't go the same way freelancer - vworker went.
I used to have an account of RentACode, a long time ago. It was mostly a good experience, considering the state of freelancing back then. When my significant otter got fired, I dug the account and handed it over to her -- it had a bunch of good reviews and some of them were for tech writing jobs, so I though it would be useful to her (she's not a programmer, she does marketing).
RAC had, in the meantime, become freelancer.com. The first thing it did was chew through the money I still had in my account -- two or three hundred dollars the withdrawal of which I had procrastinated for a long time, keeping them there in case I'd suddenly decide to take new jobs on RAC (then vWorker) again. I didn't get anything other than automated answers from their tech support, and eventually settled for that being dead money.
Now freelancer.com is a scammer's heaven. It doesn't have escrows by default, the rounding of of fees is done quite liberally, there seems to be no mechanism to stop automatic bidding (with ridiculous sums that do nothing but bring the average bid price down, since it's obvious that whatever is behind those posts is never awarded a project), and their support for disputes is unhelpful at best.
My gf is actually still unemployed and still gets projects on Freelancer every once in a while, but after being scammed twice -- with copious help through lack of reaction by Freelancer -- both her and her clients generally eschew its payment system altogether. She usually insists on a 100% milestone on Freelancer.com the first time she works with them, and then it's PayPal all the way.
The eschewing of the payment system seems to be quite generalized, because their lack of reaction and real buyer and seller protection basically means people end up paying fees for something that is then little more than a glorified job advertising website, since it otherwise fails to offer anything for the (hefty) fees they take.
Freelancer.com is a pretty sore sight nowadays. I browse its range of contract offers every once in a while; there's generally nothing for me (I do systems programming and embedded stuff -- people don't usually hire freelancers to write operating systems or make gadgets, unsurprisingly), but most of the projects and most of the bids depress me. Ads along the lines of "looking for an app expert", looking for reasonably non-trivial applications that work on a gazillion of platforms, awarded to poor people for sums that seem small even to me.