[eholk]

Firefox adopted rapid version numbers basically because the rest of the browsers did. For years Firefox was on 3.something, and they'd get questions from people saying things like "Microsoft is already on Internet 7, when are you going to support Internet 7?" If I recall right, Firefox skipped versions 5 and 6, and starting with 7 they decided to use a rapid version number scheme and deemphasize version numbers in their marketing.