Apple, via their MobileMe News blog, has just announced Live Chat Support 24/7:

We're pleased to announce that English language Live Chat support is now available 24 hours a day, seven days a week. If you encounter an issue while using MobileMe and would like to address it immediately, simply go to MobileMe support. Click on the topics at the bottom left of the page to see if your question has already been answered. If it's not, click the Chat Now button to initiate a realtime help session with a MobileMe support agent.

If you have cause to try it out, let us know how it works for you.