Why do people assume they know about something when they don't?
It does commonly amuse me when people compare different technical things when they blatantly don't know what they're talking about.
Android and iPhone's *default* app behaviour is quite similar, which means that this assumption that every app is multitasking and can cause memory leaks is highly overstated. Normally, when you switch away from an Android app, it is paused (pending removal), it's state is saved and it does no more work. The *difference* is that Android also has the ability to start a long-running fully-fledged service which can do everything a frontend app can do. Most apps don't do this, so would never be able to affect the battery. You have to specifically write your app to be multitasking to have that functionality.
And no, iPhone (<4.0) *doesn't* do multitasking, no matter how you try and redefine it. It's just marginally clever with it's state-restore ability. Try playing music in Spotify and then writing a text message. The music stops.