UPDATE: Ask and you shall receive-ish. Apple has posted a Knowledge Base article detailing (part of?) the problem (via Macrumors):
Symptoms Updated: July 22, 2008, 4 p.m. PDT. On Friday, July 18, 2008 (2008-07-18) we experienced a serious issue with one of our MobileMe mail servers. This issue is currently affecting approximately 1% of MobileMe members. [...]
