I've gotten into many a debate with people who don't even believe in washing dishes with hot water. They wash dishes with cold...saying the water doesn't even get that hot to kill bacteria, so it makes no sense. Well my dear...that's why the dish washer was invented. And if you don't have one...boiling water from a tea kettle does the same thing...just more time consuming!
I have also tested first hand the effect of hand washing dishes of a sick person vs dishwashering them (my new word). The germs don't die and you spread that cold to everyone else that uses those dishes, or that uses the sponge to clean those dishes. It never fails. When I've washed everything in the dishwasher however, no one gets sick...unless the sick person coughs on you and insists on sitting next to you (then you're screwed).
Also, for those that use the kitchen sink like a bathroom sink...DON'T DO IT. Geez! Men, listen up! No matter what you do to clean that sink, unless you bleach the hell out of it, it doesn't get clean. So, unless you want to breath in chemical fumes, please take your nasty feet and dirty teeth and use the bathroom sink to wash your feet and brush your teeth. Thank you!
FYI: Sponges are the the most contaminated items in your house, after door handles. Think about it...pretty disgusting if you ask me.
Most dishwashers today are energy savors (look for the blue sticker), unless you have a really old one, which by now has probably gone kaput, if you're lucky ;-). Even if your water heater temperature is set at 120 degrees (the standard temperature most are set at) or less, the dishwasher is designed to pre-warm the water to about 140 degrees, which is the temperature needed to kill bacteria.