iCloud has an Apple ID:
Settings > iCloud
Messages has an Apple ID:
Settings > Message > Receive At
Store has an Apple ID:
Setting > Store
Do these all have to be the same ID? If not, which ones can be different?
Or to ask this question a different way...
My wife and I both have a 4S. Can we share the same ID for iCloud (calendar sync) and Store (app sync) but not for Messages (distinct text identity)?