I think it's an overall trend. In the spring of 2005 it seemed like the domain market came back to life, and more people realized the value of domains. In the past year a lot of big portfolios have been bought up, and the great and good names are all gone now unless you want to pay enduser type prices. Quality is harder to get at a 'fair' price. More people are chasing fewer good domains. More competition at the drops. More people know about overture scores and value of keywords.
I think the domain market is just entering an equilibrium phase, where the buyers and sellers now have the same knowledge and information available to them. Sellers either want to hold onto their best names, or they want a good dollar value for their names that resellers won't pay.
Judging from the weekly dnjournal sales reports, there are still a lot of names being bought and sold for xxx,xxx and xx,xxx every week. Domains are still great real estate and will continue to be for the forseeable future. I've had more interest in my names this year than ever before. If you are starting out now trying to build a portfolio through hand regs or buying cheap domains at auction, it's a tough go. But I'm still confident the domain market will endure, and usually there is a shake up every once in a while that gets this forum going (like most recently the .mobi landrush with all the pro and con discussion has been great).