There are rumours floating around which state the main Skyrim executable (as of version
18.104.22.168) is not tied to Steamworks - or any other form of DRM - even if you bought the game from Steam. If this rumours were true, it would be the same situation as with Fallout 3, which didn't have any DRM on the main executable even though it included SecuROM on the game launcher.
Another set of rumours is that the Russian-language version distributed by 1C in the CIS is not tied to Steam. In fact, so the rumour goes, it doesn't even have a serial number usable on Steam, so it isn't registrable there even if one wanted to do so.
Testing the first rumour would require one to save the Skyrim folder and its registry keys, uninstall Steam, then try to see if the game would still run. Testing the second rumour would need someone from the CIS to get the 1C-distributed version of the game and verify whether it is true or not. Both simple test - but I can't do either of them at the moment.