By default, modules generated with features are created with a version string in the *.info file.
I think the convention is to increase this version number when the feature changes.
In a distributed development work flow with a lot of merging, a linear version increment is not a useful model or metaphor.
Is the version number, and incrementing it, useful or necessary for anything?
I work in a project where until now almost none of the features has version number. But recently a colleague reported problems reverting the features on deployment, if they don't have a version. Of this could be pure concidence, and caused by something other than the missing version number.