AdSense Competitors?

With AdSense such a huge money making machine for Google, I would think other search engines would start rolling out similar programs. Did a little poking around (well Rustybrick pointed me actually), and found out that Overture does have a context sensitive ad program, but it's only open to sites with 30 million page views or more. Seems strange to me to put those sorts of restrictions on it, as it's an automated system (at least if it's done like AdSense).