If a startup idea were so obviously good, it would’ve been done already. This means it's probably a bad idea to judge a startup based on your first impression. For example, Twitter looked like a stupid blogging service (140 character posts?!) when it launched. If you're interested in evaluating the potential of your idea, try answering these questions honestly in a Google Doc. It's the first thing I do whenever I come across an interesting problem.

Y Combinator

1. Describe your company in 50 characters or less.
2. What is your company going to make?
3. Why did you pick this idea? Do you have domain expertise in this area? How do you know people need what you're making?
4. What's new about what you're making? What substitutes do people resort to because it doesn't exist yet?
5. Who are your competitors, and who might become competitors? Who do you fear most?
6. What do you understand about your business that other companies in it just don't get?
7. How will you make money? How much could you make? Give your best estimate.
8. How will you get users, and if you're a marketplace how will you overcome the chicken and egg problem?

Sequoia

1. What is your company's purpose?
2. Describe the pain of your customer — how is this addressed today and what are the shortcomings of current solutions?
3. Explain your eureka moment. Why is your value prop unique and compelling? Why will it endure? And where does it go from here?
4. Why now? Nature hates a vacuum — so why hasn't your solution been built before now?
5. Identify your customers and your market. Some of the best companies invent their own markets.
6. Competition and alternatives — who are your direct and indirect competitors. What's your plan to win?
7. What is your business model, and how do you intend to thrive?
8. Team — tell the story of your founders & key team members.
9. Financials — how will you finance this?
10. Vision — if all goes well, what will you have built in 5 years?

Peter Thiel

1. Can you create breakthrough technology instead of incremental improvement?
2. Is now the right time to start your particular business?
3. Are you starting with a big share of a small market?
4. Do you have the right team?
5. Do you have a way to not just create but deliver your product?
6. Will your market position be defensible 10 and 20 years in the future?
7. Have you identified a unique opportunity that others don't see?

As always, I'd love to help if think you've discovered a problem worth solving.