As a Vonage user, one of my pet-peeves was having to dial a full 10-digits - even when dialing the local pizzeria, the local chinese restaurant down the street, etc.
I never understood why Vonage or any VoIP voice provider for that matter couldn't simply detect your local region based on your VoIP phone number and then simply pre-pend the area code for you, allowing you to dial a phone number without an area code. As a computer engineer, I know it's so simple to program it's ridiculous!
check out the whole story here:
Lingo Internet Phone Service Offers 7-Digit Dialing Option