In the store-bitmap-in-array-case..:
Why would you want that, unless it's a workaround for not having to access the harddisk? There are smarter methods for that..
It's useful if you have to look up a pixel value and check to see if a pixel is at a certain co-ord, without having to use a read pixel command, which would be slower. Even banks are slower than 2d arrays in general.