I'm surprised no one has brought up the power cost point yet. I have a couple services I'd like to be up 24/7 and paying for hosting on them is actually cheaper than I'd be able to do from home just due to the cost of electricity where I live. Plus I've had quite a few ISP outages, but my provider, as far as I can tell, has been up 24/7/365 in the few years I've been paying them.