Read original post by Paul Laberge at Canadian Mobile Developers' Blog
One of the more complicated concepts in phone development, regardless of the platform you are targeting, is multi-tasking. The nature of a mobile device is to be resource-limited. It’s not a PC where you have a significant amount of CPU, memory, storage and other assets to tap into in your apps and games. The result is that you have to be wise in how your apps and games use resources on the phone.