There was a thread recently in one of the blogs that I follow, where readers discussed the virtues of keeping a backyard chicken coop.
Three families that we know have them. They all boast the benefits of keeping chickens. The most obvious is fresh eggs, of course, but other benefits include pest management (think insects and lizards), good fertilizer from their droppings, plus the novelty of having a chicken as a pet.
The downside is that they destroy your yard; plants picked down to nubs, all the grass scratched away to bare dirt, and they will eat anything. This was confirmed by our friend who was barbecuing recently. After repeatedly shooing them away, he eventually had to herd their three chickens back into the coop for their own safety because the chickens kept trying to hop on the grill to steal food.
I asked him what he was cooking and he replied, "Chicken. And not even one of ours! Although with the way they were trying to get at the grill, it very well could have been..."