Official word from Google on the mysterious disappearance of many apps from the supposedly intervention-free Android Market yesterday:
The demo devices give an early version of the Market since it hasn't been launched yet. We needed to be sure that a few of the 3rd party apps are final for consumer use in the Android Market when the T-Mobile G1 officially launches on October 22nd. We're replacing the preview applications with final versions today. After October 22nd, developers will be managing their own applications.
So apparently just a little pre-release cleanup; after tomorrow, though, Mummy's going out to run some errands so you're in charge now, devs.