A lot of software is developed via some sort of agile software process these days. This means a new version of the software quite regularly, released on a time basis rather than a feature basis. This is what made version numbers meaningless. There are three common solutions:

time based: Ubuntu 12.04

increment the major number: Chrome 31

increment the minor number, never or rarely changing the major numbers: Linux 2.6.39

None of these solutions work well.