Apple has posted a support document which uncharacteristically details many changes the company has recently made to MobileMe. Apple explains why it is being so open by saying:
Since server-side updates are a bit more innocuous than a standard software update to Mac OS X or Microsoft Windows, it's easy not to notice that updates are occurring. Usually the only hint of these updates is that things just "work better"
MobileMe is .Mac's replacement service and when is launched in July suffered serious issues for several weeks.