[ghempton]

I don't think that is necessarily true. Majority of freelancing sites are geared towards overseas outsourcing and portray the value proposition to companies of adding money to their bottom line. This naturally makes it hard for US based developers to make market rate on these sites.

Shameless self-promotion: I am a co-founder of grouptalent.com which is geared towards high-end freelance developers and rates generally trend toward market.