Simmer down folks -- everything is going to be a-okay. Yes, 'tis true -- Microsoft has indeed scheduled for Xbox Live service maintenance and Zune service tweakage to take place at the exact same time this coming Monday, but it's probably not worth losing your mind over. In fact, Major Nelson goes out of his way to affirm that "when [Xbox Live] service returns, you will not have any new features and you will not have the new Xbox experience update." Point being, your Zune Social, Zune.net forums, all of the Zune Marketplace and Xbox Live services will be offline for up to 24 hours (48 hours for the Zune suite) starting at 12:01 PST on September 29th, but don't expect a Zunephone to pop out of your now-forgotten HD DVD add-on when things come back on. Or you can, but we'd be prepared for unprecedented disappointment.
[Thanks to everyone who sent this in]
Read - Xbox Live down time
Read - Zune services down time