This happens all the time, but here's an example:
- libgdal-dev, versus
Why are some packages named with the version number and others are not? This seems to happen more with libraries, so that might hold a clue (other packages depend on specific versions?), but I recall it happening in other contexts also.
Finally, what are the implications of installing a numbered version when that version becomes obsolete? If I install libgeos-3.3.3 does it not get automagically upgraded to libgeos-4.5.0 when 3.3.3 is obsolete?