[Pyramid*]

I can understand friendships forming over time, people swopping email addresses, and then taking that a step further to passing phone numbers - but I think there has to be a certain degree of safety involved as well as commonsense.

Much of that can only come from building up rapport / and trust. (which to be fair on 'both sides' .., I've seen trusting friendships build - and have also seen those who are meant to be 'best buddies' going around stabbing each other in the back, on the flip of a coin).