[mattmiller]

Do you feel like you truly tested any of these ideas? If so how?

I have built something that I think is good, but has not taken off. I don't think it is a bad idea, I think it is an untested idea. I would hate to drop it without anyone ever seeing it.

[mojombo]

With a lot of effort I think they all could have been successful. But when you have to work your day job to make a living, you need something you can bootstrap on the side without investing huge amounts of unrewarded effort up front. That's why I like to start a lot of things and then see what happens. Sometimes I give up on an idea simply because it becomes uninteresting (e.g. retail). With both Gravatar and GitHub, it was almost immediately obvious that they were ideas worth pursuing. They got people excited, and I could easily gauge the interest by tracking signups. If you're not seeing signups, it means something is wrong and you'll have to decide how much effort you're willing to invest in order to fix that something. Without knowing the details it's hard for me to give any more insight.