You should be aware the ppc decline seeems to be industry wide and not limited to Sedo, Namedrive, TrafficZ, etc. I do not use parked pages much but can tell you from first hand experience my YPN and Adsense stats are also down over the past few months, with a steeper decline ongoing over the last couple weeks.
Since Google and Yahoo are supplying the ads to most of the parking firms the net result is obvious.
P.S. The first days of Oct have been about the poorest 8 days in a row I ever recall seeing going back more than 3-years. With that in mind, I doubt the parking firms are the problem as the main issue is more than likely elsewhere.