These days, most entrepreneurs I talk to understand the importance of speaking with customers before building a full-blown product. They’re getting out of the building. And that’s great. A few years ago it wasn’t like that at all.

But unfortunately, I often speak with entrepreneurs that have only talked to one or two customers. That’s not nearly enough. The danger in speaking with too few customers is that you bet too much on too little data. If the first customer you speak to loves your idea and you put blinders on to go build the solution, you haven’t eliminated any real risk. You’ve just found one potential customer. Chances are you don’t even understand the problem well enough to solve it.

A customer that says, “That sounds cool,” or “That would be really useful,” is a lot different than one who says, “I’ve tried solving that problem in a few ways, and looked at five different solutions, none of which really addresses my problem.”

You need to find out if the customers you’re speaking to have ever tried to solve the problem on their own and/or if they’ve gone out and looked at other solutions. If they haven’t done that, there’s a very good chance the problem isn’t big or painful enough. Ask them straight up, “How have you tried to solve this problem before?” Don’t be shy about it.

Consulting companies that want to convert themselves into product companies run the risk of building a product off too few customers. They get hired to build something, and assume there are no alternative solutions that are good enough. They deliver the solution and then decide that there must be a whole bunch of other customers out there that need the same thing. Maybe. But maybe not.

In my experience you need to speak with at least 10-15 potential customers before you can see any significant patterns and get any real clarity. After 10 or so interviews you should have a good sense as to whether or not the problem you’re proposing to solve is important enough.

One customer doesn’t automatically represent a worthwhile market. It’s just one customer. And you need to know why they’re a customer (or a potential customer) before making the big assumption that they represent a full-blown market. If they became a customer because they didn’t know any better (never bothered looking for something else), or they’re your friends, or some other non-replicable and scalable reason, you could be in trouble.