There was a period near the beginning when SD had a stark interface and wasn't very nice looking. He fixed that and now I'd say it would be hard to make a clone that could pull users away from SD. It would have to be different and superior in some way that many users would prefer it.

Or I'm wrong. It just could be the same and better promotion could attract new Bitcoiners. If things go well in the future the current user base is < 0.1% the eventual. And 1% of new user adoption could be better than 50% of current market share. Same goes for eWallet services.

My original comment above was more related to identifying something new which people will want to use before it is successful. It's not nearly so hard to detect them after they're successful. My real failing is not being much of a businessman. Any true businessman wouldn't care about being original if being a copycat could make as much or more money, which would be like saying "I won't be a land developer" because it's been done before.

But I doubt SD is the Bitcoin "killer app". Or I hope there will be something better.