Protect Your Ideas
Even if you have the ideal domain already, chances are you need to protect your brand by also registering different TLDs (.net, .org, etc.) or similar variations.
Competitors will grab them if you don't!
Email Matters
Free email accounts don't exactly inspire confidence in people browsing your product or service.
Make sure they know you're a professional with a you@yourdomain.com email address.
Look Your Best
Appearances DO matter, and on the web first impressions can quickly become "last" impressions.
Give potential customers the right impression right away by using a domain that's all your own.