My apologies for being unclear. I was using the terms as synonyms of each other. Every product is a project.

> I'll gladly stick my head in the sand and assume the existing employees can take over in the event a person disappears.

My point is that this even in large companies, it's is far from unheard of that the entire product relies on a single individual's knowledge. If that individual were to go away, the product cannot be changed until someone else is able to come up to speed enough to replace that person. It's probably more likely to happen in a very small company, of course, but big or small, if it happens the effect is the same.