You just can't give a meaning to version numbers anyway, because each vendor has completely different conventions, which might be dictated by the marketing department. Examples:

• Java: after version 1.4, you have version 5; there are pretty substantial differences between "minor" version numbers.
• OS X: they advertise the difference between 10.3 and 10.4 as a monumental event, which is not what one would expect just by looking at the version numbers.
• Several historic Microsoft products: version 1 was completely useless; version 2 was an alpha version; version 3 is almost usable, and version 5 or 6 may actually be pretty good...
• CPAN: many authors start at 0.01 or 0.1, and most of them never make it to 1.0, even for some very stable modules. There is usually a belief that a change in the integer part of the version number implies large changes with break of backward compatibility. It is very rare to see version numbers greater than 4.0 (except for some that use something like 20051028 as the version number).
• Pugs: approaches a certain value (2pi) asymptotically.