God and keeping up with friends

So last night gave me the opportunity to IM with a good friend that I've not seen in quite a while. But he's very good at IMing me whenever he sees me online, and always uses the opportunity to keep up with me.

So this brings up a good point: what does God call us to when we enter into a friendship? And is there a difference between friendships with fellow believers versus non-believers? What does it mean to keep up with your friends? As a Christian, what does it mean to be a friend?

Weigh in with your thoughts...