True. However, since the iPhone allows the entire storage (e.g. 16 gigs) to be treated as internal memory, the opening and closing of applications is not nearly as time consuming as on the Android platform.
There are advantages and disadvantages of each approach.
Since when is opening and closing apps on Android time consuming? It takes a split second to open most apps. In fact I see no difference in the time from when I select the app to it opening between my Droid and my friend's iPhone 3gs. However because I can long press and switch between the last running apps easily, I can often switch between used apps quicker than he can.