[lsd5you]

Erm surely ability is important as well. Programming is no different in this regard to pro sports - some people have more talent (which probably in turn breaks down into innate attributes, determination and learning opportunity earlier in life).

[codr7]

Ability comes from practice, there really are no shortcuts.

Most of the difference seem to be in motivation.

[collyw]

Some people really don't get programming while others do.

When I studied at university many years ago, my course had a reputation for being tough. Before the course started properly, there was a three week intensive Java course with an exam at the end. They suggested that if you didn't pass the exam, then it probably wasn't the subject for you. A couple of people failed that exam and continued with the rest of the year long course anyway. Those people did struggle and I don't think any of them passed.