what makes a good product?

For my money, a good business idea needs the following:

1. A problem (a.k.a. a need)
2. For that problem to be common enough to create a market (i.e. there’s no point creating a product if you’re the only one who’ll ever use it – I find this is very rarely the case though)
3. For their to be a “choke point” in the market (i.e. who is the common person that people with the problem I’m trying to address would be talking to?)
4. For there to be a way to quickly communicate the benefit of your idea (I don’t mean the vehicle by which you communicate, I mean the message. Can you succinctly sum up your value proposition and get a potential customer onboard – The Twitter Challenge is to do it in less than 140 characters and not have it blend it with everything else.)

Anything else that I might have missed?