The other point to remember is that Russia most likely has its own red-lines and that some may have been triggered already.

Moscow lost control of Ukraine during the Great Patriotic War and I suspect they do not want to see the former Soviet state simply swing into the West's sphere. That would put the front line of the East-West divide right back at the heartland of Russia as it was in 1940/41. Russia's strategy for security seems to depend around the inevitability of the state's centralist weaknesses being mitigated by the immense distances and buffer-zones of the former Soviet states. Pre-empting Ukraine becoming a part or an associate of NATO is, if I were to make an uneducated guess, the driving calculus for Moscow right now.

In the same way that the American presence projected into Iraq served as a means of influencing Iran and Saudi Arabia back in '03, I suspect that Russian presence projected into Georgia in '08 helped serve, in part, as a means of influencing Ukraine. I think that Russia isn't willing to accept such a fundamental change to it's geopolitical assumptions given the potentially enormous consequences of losing Ukraine to the EU/NATO sphere (and, while the likes of Orange revolution and the recent ousting of Yanukovych are baby steps, they do have huge potential for changing the trajectory of the region).