Pros of asking for a Facebook over a phone number:

-Can't get a fake Facebook like you can get a fake phone.

-Have access to information and pictures of her.

-Most women are more comfortable giving their Facebook over their phone number oddly enough.

-Only option for international girls

Cons:

-Perhaps a friend vibe associated with it? Perhaps not?

With Facebook messenger it is really easy to message girls back and forth, plus you see their picture associated with their account.

Am I missing something here or is just exchanging Facebooks much more valuable than exchanging phone numbers?