Many times what I have seen in the field is a database is created starting to use small increments(100MB, 200MB), and then all of the sudden, the application starts to be used extensively and DBA starts to use 2GB increments.
Well, you can start to run out of device fragments within a DB, and may want to clean it up and reduce the fragmentation of you sysusages.
So, if you created you DB as follows:
DATA1 200
LOG 500
DATA1 200
DATA1 200
DATA1 200
DATA1 200
DATA2 1000
DATA2 1000
YOu can create your new database as:
DATA1 200
LOG 500
DATA1 800
DATA2 2000
Load you dump, and you are off and running.