Who's writing down the number?

Can we maybe have some guidelines for billboards? Like phone numbers. How often do people write down the numbers they see on billboards?
My guess is not very often, even if that number is easy to remember, like this one for what appears to be a crisis pregnancy center hotline.
We're trying to drive. Ditch the phone numbers. Websites are far easier to remember. And while you’re squeezing your web address on that billboard, I can save you some space: drop the "www."
We all figured out about 10 years ago that if you have .com, .org, .biz or dot anything at the end, that means we can find it online.I'm no art director, but I think I just made this billboard better.

Taken from: Where's my Jetpack?