Sina and Sohu are two of the biggest portals in China so it makes sense that they be the first to "register". Not that it will have much effect though once the populace gets more contact with the outside world via the internet.
The government is already blocking access to some sites, (whilst I was there I couldn't get access to one US site to download FileMaker Pro files although I have no idea why that particular site would be on the no-no list), but any savvy citizen with proxy knowledge could bypass that very quickly.
Unfortunately the article infers that this is part of a requirement for China to enter the WTO - not so. China tightened internet laws including foriegn ownership but promised concessions to foriegn ownership AFTER it joined the WTO. Anyone afer more info can check out my post in the forum here [webmasterworld.com] for more info.