Email is such a funny thing. People hand you these single little messages that are no heavier than a river pebble. But it doesn't take long until you have acquired a pile of pebbles that's taller than you and heavier than you could ever hope to move, even if you wanted to do it over a few dozen trips. But for the person who took the time to hand you their pebble, it seems outrageous that you can't handle that one tiny thing. "What pile? It's just a pebble!"
as quoted in Clay Shirky's 'Here Comes Everybody', p.94