A few interesting quotes from successful entreprenurs on how they perceived competitors in their startups.

You can never be paranoid enough about the competition. Assume they're all out to get you at every turn, that they're smarter, richer, quicker, and better looking than you are. Live in fear of them eating your lunch -- Matt Blumberg, Founder & CEO, Return Path

Even in the face of massive competition, don’t think about the competition. Literally don’t think about them. Every time you’re in a meeting and you’re tempted to talk about a competitor, replace that thought with one about user feedback or surveys. Just think about the customer -- Mike McCue, CEO Tellme Networks, Former VP of Technology Netscape

Competition starts at $100 million -- Glenn Kelman, CEO Redfin

Being fiercely competitive is fine, you can hate that your competitors are performing better than you, and you can be hyper-paranoid about what might happen to your business, but the best way to compete in the market is to focus on those things you can strive toward independent of what anybody else does -- Dick Costolo, Founder, FeedBurner

Assume you have 30 competitors. Assume half of them have more money than you. Assume they’re ahead of you. Don’t worry when they launch before you do. Every overnight success story is the result of years of sustained, focused execution. If you want to be #1, ignore the competition -- Nivi, Entreprenue in Residence at Atlas Venture