After the South China Sea earthquake, at least 6 international cable connected with China is damaged. In China, we cannot login with Windows Live Messenger or Yahoo Messenger. We still can use Google Talk and Tencent QQ, but friends in foreign countries cannot login with Tencent QQ for it has no server outside China. So, Google Talk become the only choice, if you want to chat with foreign friends.
How about Skype? It's a P2P client. Yes, I can login with my Skype, with a very unstable connection. It disconnects every few seconds, and connects after another minute. I cannot chat with this unstable connection, so I gave up using Skype.