[IndieDevClub]

As Paul Graham says Startup = Growth. If you think your project has a large enough market and can acquire users exponentially then it could be a startup.

On the other hand if you need to do a lot of work to acquire more users or it's in a small niche, then it can't scale and wouldn't be a startup. What's interesting is you can turn a side project into a startup. You just have to figure out how to scale. That's why Paul Graham says to do things that don't scale. The hard part is making something people want. If you figure that out, there might be some way to scale it.

This week I'm trying to put together a club where people can discuss their side projects and early-stage startups. It's called Indie Developer Club. If anyone is interested see my profile for the link.

[amjd]

Good point. I believe growth is one of the most important factors. Though in many cases one wouldn't have a clear idea about it as the idea might change over time (think WhatsApp).