Faith + Reason = Truth

The short answer is yes, as this video at Guy Kawasaki's site shows.  Two of the startups featured at this VC panel over the weekend are single-employee ventures, so watch and learn, folks!  As for trying to get things done by yourself, from personal experience, you will need:

1. attention span and commitment to keep at it
2. energy
3. passion
4. resourcefulness
5. giving as much of yourself as you can in the form of freely participating and contributing to other people's successes
6. money helps, but I don't have any and am progressing nicely