I thought once out of the app, the app is shelved until it is opened again and picks up where it left off. When I open up Processes, I see a bunch of running apps and my free memory down to about 65mb. and dropbox refuses to go away. Is this normal?
I always like to keep my app drawer clean and I always ended up closing all my apps except Phone, Mail, SMS, iPod, and Safari.... Unless I need that certain app to run (eg: Skype call or Pandora streaming).
I've been doing this since the iPhone 3G days, continued when I moved to Android where I always kill all my apps, and now with iPhone 4.