When you look at the most successful startups of the last 5 years, one common property is that they built not just a polished product, but a great distribution strategy that was a natural fit. In some cases, it was a viral marketing scheme like Dropbox's - sign up your friend, get free storage. In others, it was that the creators had identified a segment of potential users that would immediately adopt the product - think about how Facebook forcibly created an account for all Harvard undergrads on day one. Gilt came to own New York by spamming women in their core age and income group.
In a way, coming up with distribution ideas is more fun than coming up with startup ideas, partially because it is more constrained: You have to invent a scheme that's not too expensive to operate, socially acceptable, and targeted to the demographic that would use your product. I encourage you to think distribution first.