Beta, as explained to the masses

Slate this week is belatedly celebrating Gmail's fifth anniversary (April 1) in exactly the proper fashion, asking what the heck beta status even means when it's applied to a service with over 100,000,000 users. The Explainer column gives a safe-for-civilians overview of what "beta" has meant in the past, and dips a toe into more recent philosophical debates ("Beta bad!" "No! Beta good!"). It'll be interesting, of course, to hear the thoughts of our more techish readership: Is years-long beta a subversion of the concept? And are we all relieved that Flickr's "gamma" schtick didn't catch on?