ROFLMAO. Actually it is not the rise of the BTC-E. It is due to the decline of the other exchanges.
BTC China volume has declined by more than 50%, and Mt Gox has also declined considerably. BTC-E is having near-100% market share in the CIS nations (Russia, Ukraine, Belarus.etc) and the volumes haven't changed much. Also, I have heard that BTC-E is keen on expanding to China.
why is there only one exchange for eastern europe ? or maybe i dont know the others...
bitstamp is in slovenia so I'm sure they server eastern europe as well. btc-e seems to have found a great niche i.e. people trading litecoins when other exchanges have ignored them, even when (mtgox for example) promised to support them.