Hello sedditors.

With the advancement in technologies like Facebook Messenger, WhatsApp and the like, I was wondering that is the art to get a number from a girl relevant enough?

For example, say thay I met a girl from a party. I knew her name and turns out she is my friend's friend. Naturally, her name would just pop up on the friends' suggestions on Facebook. I would just add her as a friend, and if approved, initiate a conversation through Messenger.

Or, in WhatsApp, I would've just known her number though, say "Biochem class 16/17". Effortlessly, I can just find her number and start a conversation.

What do you think? Is it relevant? Or, to an extent, is it morally ethical?