This was just addressed today by Josh Coates of Mozy.com who talked to a small class of CS students. He said, "if your idea is good then there are six other guys out there working on it full time. If it's not good then don't work on it."
On the other side I just finished the Chapter in Founders at Work on 37 Signals. David Heinemeier Hansson created BaseCamp and he only spent 10 hours a week on it. He was the only programmer working on it too. Designers did help out but they only gave a third of their time too. But he said this lack of time was the greatest gift to the development of Basecamp. It helped focus his view on what they needed, and it forced them to make tough decisions about making less software all the time. When you have a lot of time you just get tempted to try to do it all, or at least do too much. So maybe if you don't try to do everything and just the essential then it might be a gift too.
37 Signals embraced the constraints that were forced upon them.
So the short answer to your question is . . . it depends. But it's still a question that needs to be asked.
Also, if the market for your idea is very very good, and the company is offering a service, then this might work. You are already selling the service by now, within your limited time, and the competition doesn't care much as there is such a huge market for your idea. But these are not the conditions in all the cases...
I like the notion of how constraints help. I think that's pretty key, prevents feature creep and the rest, which could easily overwork a full time team that gets to ambitious.
On the other side I just finished the Chapter in Founders at Work on 37 Signals. David Heinemeier Hansson created BaseCamp and he only spent 10 hours a week on it. He was the only programmer working on it too. Designers did help out but they only gave a third of their time too. But he said this lack of time was the greatest gift to the development of Basecamp. It helped focus his view on what they needed, and it forced them to make tough decisions about making less software all the time. When you have a lot of time you just get tempted to try to do it all, or at least do too much. So maybe if you don't try to do everything and just the essential then it might be a gift too.
37 Signals embraced the constraints that were forced upon them.
So the short answer to your question is . . . it depends. But it's still a question that needs to be asked.