Not at all. We've had this happen quite a bit. The key is making sure that people have the problem that the product solves (and that they really hate the problem, or it costs them quite a bit of time or money, etc.). That's what you're really looking for: if people would pay to have the problem solved. That's indicator #1; not necessarily if there are existing solutions out there.

While it is harder marketing something that has no existing solutions like it, we've found that it's definitely not impossible.