How long have you been using your kitchen washing up sponge? Most probably more than 3 days and, if this is the case, it will be by now be teaming with millions (I think the actual number is around a trillion) of bacteria. The main culprits are E. coli, Salmonella and Campylobacter, and these are the nasty little fellows who can give you food poisoning. In fact, nearly all food-borne diseases in the western world are caused by bacteria that is happily lurking in our own homes.
Just like a house party usually ends up in the kitchen, this is the room where you'll also find most bacteria, as this is where the food is. The sink area is a particular favorite and bacteria even gets into all the teeny nooks and crannies in the stainless steel surface. Here, they produce goo that sticks them in place making it really hard to get rid of them.
The washing up sponge, however, has to be the most disgusting thing in your entire house. And I know you probably wash it out well, but believe me, you won't do it well enough to completely get rid of the bacteria (tip: if it smells bad then this is bacterial growth and Mr Sponge needs to go in the bin). And for all you people who insist on wiping the surfaces with the same cloth to 'clean' them after use - you are spreading dangerous bacteria over everything. Scientists have actually studied how bacteria can be spread around a kitchen and the results aren't nice. To start with, up to 10 million bacteria have been found in 1ml of skanky water squeezed out of a kitchen sponge and nearly all sponges will harbor bacteria capable of causing illness in humans. If this bacteria gets onto your kitchen surfaces or hands it can be transferred to your food. Wait a few hours, then its off to the loo as the diarrhea and vomiting kicks in.
In fact,studies have shown that your toilet bowl is usually a lot cleaner than a lot of 'safer' areas in the house. It gets flushed regularly after all. After the washing up sponge, the kitchen sink is the second most horrid place in the house, followed by the bathroom sink, then the kitchen taps.
It will never be possible to have a completely germ free home - bacteria and everywhere and most of them can quite happily live with us without trying to kill us. But we can do something about our kitchen sponges. You can soak in bleach and run the risk of getting bleach in your food, which just isn't nice at all. Or you can microwave Sponge Bob on high power for one minute every day and this will kill everything living on him. Companies are currently working on developing a sponge with anti-bacterial properties and this will probably make quite a difference to the food poisoning rates.

