Quite rarely, to be honest. One of the things that prevented me from getting Twitter was the (mis-)conception that it would just be people tweeting stuff like "OMG I MADE TOAST! lolz" all day. Thankfully, most of the people I follow come up with more important stuff to say (most, not all), but it means that when I do tweet something, or update my Facebook status, I try and make it relatively substantial. People don't care if I forgot my keys; people DO care if I happen to bump into Keira Knightley in the street which so totally happened to me a few weeks ago and was my most popular Facebook status in a long time. It's knowing when to splurge and when to keep quiet.