Mac OS X Beta Expiration Date
According to Apple's Mac OS X Beta FAQ:
Mac OS X Public Beta will expire on May 15, 2001. At that time the software will stop working, and you will need a bootable Mac OS CD (not the Mac OS X Public Beta CD) to gain access to the contents of your hard drive or to reset your computer's startup disk.
While this is somewhat understandable for Beta software - I'm not sure everyone is aware that they are really committing to buying Mac OS X Release when getting the Beta. Well - at least we know Mac OS X 1.0 will arrive by May 15, 2001 (or there will be a whole lot of angry Mac users :)