I think that's exactly the point: while those myriad of technologies allow you to mitigate some of the downsides of distance, they still don't have the accidental factor that random hallway conversations have. I can walk by someone having a cool conversation in the break room and join in. I can have lunch with my coworkers and seamsly switch back forth between work discussions and personal ones. And I don't have to follow anything, check any mailboxes, or type any responses arbitrarily limited to a certain number of characters.