here is my conclusion: whatever you do, you will always end up having problems with those kind of site.

Either the escrow can be reverted, or the site side with the "employer", how about installing that odesk thing that take a screenshot of your desktop every few minutes ? and on, and on, etc.

I worked as a freelancer without such web sites for 10+ years (both in France and UK), either solo by networking etc. or via an agent that was finding clients for me in exchange of a 20% commission (yes that's not a typo) and this was 10 times better that any freelancer web site.

So what is the real problem ?

you (the freelancer) are actually the product

so called "employers" can play the game "let's find the cheapest product" (eg. let's hire a freelancer that can work for $8/hour in some other country)

you can not do any margin with a competition toward "cheap" either you invoice per hour, so even if you do the job faster than someone else you just invoice the actual hours, or you bid on a fixed price which is also a race to lowest amount of money.

It is absolutely a no-win situation

as an individual or a company wether you're building web sites, applications, mobile apps, etc. all those things have high values it is absolutely OK to invoice more that the time it took you to do it eg. make a margin to make a living

also those sites tend to concentrate "bad clients" eg. the one who don't understand technology, why it cost so much to do this, why you can not build something complicated in 10 minutes, etc. exactly the kind of clients you try to avoid at all cost