Commenting from the buying perspective, I think sites like Elance, Guru, RentACoder, ODesk, etc. are essential cost-effective resources for startups, non-profits, and increasingly larger businesses as well. Even great for personal stuff - like invitation designs, T-Shirt designs for sports teams, etc.
I`ve used Elance successfully as a buyer in all of those contexts - a logo for my son`s rock band, a special invite for my Mom`s BDay, a logo and letterhead for a non-profit, a business card design for my son`s micro business, and as as a way to generate paid logo concept ideas for my new startup. For a detailed post regarding how I went about this latter project and results, see here.
I have been very pleased with the results and the cost (even after not awarding based on price). Not surprisingly, performing thoughtful due diligence on the providers, taking the time to carefully articulate your requirements, chunking the work up into smaller, phased and less risky deliverables all help to increase the probability of a successful outcome.
These sites are not perfect and are constantly improving, but I highly recommend trying one out on a low-risk project and making your own assessment. I suspect you`ll become a believer.