You’re better off simply investing directly, instead of through your electricity bill.
Invest, say $1000 when Mt.Gox* is ddos-ed. For some reason everybody decides to SELL SELL SELL if Mt.Gox* webservices have a bit of latency. During this bit of latency, the stock crashes down 70-80% in value, and history tells us that it slowly regains its value in the period of a few days. So, within a week you should have $3500-5000, which is a nice profit.
Some day those idiots will learn, and either the stock exchange doesn’t crash upon a ddos-attack, or people will lose faith and the value will not recover. Until then, we might just as well exploit it. It’s risky, but if you have money laying around that you could just as well burn, you may want to get into these get-rich-quick schemes, and let the honest hard work (bruteforcing hashes that start with N zeros) be done by others.
* Magic The Gathering Online Exchange - trustworthy stuff, aye!