Well for quality US traffic from type-in I know for an absolute fact my domains make waaaaaaaaaaaaaay more with parked.com than sedo. I will put up $10,000 cash to anyone who want's to bet against this if you want me to perform & post a controlled experiment with known steady traffic generic domain names from several different industries. Amongst several factors for this, one of the major one's being the credit/payment for multiple clicks at parked.com when sedo only pay's you for one even if your "credit card" or "credit report" visitor clicks 10 different links...now tell me that is fair to you as a customer? Same thing for other google parking feeds as far as I know..
Today last year, (12 months ago) my daily RPM at parked.com was $216.01 RPM which was about the same most days then..the average overall finalized RPM this week in 2009 is running at $194.04 with about 25% less traffic than I had this time last year due to less traffic as some names were sold/removed/developed, etc...not really a huge difference when you do the math on it and the longer term comparisons are the same...value changes if any have been nominal and more people are parking at parked.com than ever before because the payouts are so good and usually way more than sedo. In fact, most people LOVE to buy domains parked at sedo just like I routinely do so that you can move them to parked.com and make sometimes 25% to 75% (or as I have seen on some 200%+) more overall a month with them because of better keyword control, layouts, payouts, & counting of multiple clicks (if you have the traffic & clicks) Obviously on very small portfolio's or low traffic numbers any slight fluctuations will seem extreme compared to the larger ones that are actually better indicators on any current trends. The trend right now at parked.com is great. Steady, reliable, & easy to use with payouts twice a month along with more templates & options than ever before and the best customer service on the Internet.