Easy fella, it's not a flaw and you missed a subtle point about what SirGaz said.
Android is designed to keep apps around rather than kill and this does indeed allow for multi-tasking and other cool stuff. Android kills processes as resources are needed. Now, if you're complaint is that android isn't aggressive enough in clearing resources, I'd agree with you, some option to set this would be nice.
Also, (and this is not aimed at you directly), when people talk about processes running in the background, it doesn't mean they're consuming the resources they do when they are running when you are actually using them. When you press the home button, the running app is told and is given a short amount of time to do whatever it needs to. Usually this means storing some information so that if you go back to the app, you can carry on where you left off. The app isn't killed but it's not running either, i.e. it is consuming some resources but not the same amount as when it is running. If resources are needed badly enough, Android may kill the process totally. I think this is where people's problems are, Android doesn't clear its house often enough. Could possibly be controlled by an option somewhere; it may also be one of the tricks in the custom ROMs (but don't know if that's true!)