Not necessarily. I had a few bad experiences with vWorker, freelancer and other market places. oDesk is slightly better than the lot. In oDesk the initial 30 days was working on low priced contracts and couple of times with clients who didn't pay. It was a little painful learning.
But, then I got a little better at identifying the right set of clients and now the I set rate at $33/hr and most of it in hourly contracts that are guaranteed payment. I also take fixed price contracts from clients with whom I have existing relationship. Many guys I know are charging $60/hr and having a good practice.
The thing in the initial phase you come across a lot of noise and as you find out the 1-2 good clients from the 10 shabby ones, you get repeat business from them.
The difference between freelance marketplaces and direct sales is that in the former the clients have a real need, while in the latter the we have to convince the potential leads of the need to have a good website with proper attention to typography, speed and ux.
I typically use PHP and many of my sites are built on Wordpress. I have previously done Web programming before realizing that it can get pretty expensive in terms of maintenance. With quality, premium plugins and themes, you can get a quality site out in about 6 hours and charge $300. I tweak the CSS and PHP of the existing themes to get close to the customer needs and have built a KB and a process internally to reduce the full site development 6 hours what it used to take 25 hours or more.
That is working good so far. It is also easy to maintain, I have WP_MU setup and can update a large number of sites in parallel.
Which marketplaces are better or worse than others? Is oDesk different from the crapfest that is eLance?