What is the largest amount of objects I can put in my NSArray?
NSNotFound is defined as NSIntegerMax (this value changes if you are on a 32bit or 64bit system)
NSNotFound is also the result you get when you do a
[nsarray indexOfObject:obj]
and no object is found.
If you do not run out of space/memory I would say that this would be your limit.
http://developer.apple.com/library/mac/#documentation/cocoa/reference/foundation/Miscellaneous/Foundation_Constants/Reference/reference.html