Exactly this. I've had as many "serendipitous hallway conversations" in the last year as I had in the years before - just this time, they happened on IM, on videocalls, and in code review comments.

A small group of co-workers willing to sometimes go off a tangent in a conversation is all it takes. Doesn't have to be face to face, much less in a hallway or in front of a water cooler.