All I ever saw was "This iPhone cannot be backed up because there is not enough storage".
don't get me wrong. in general i think apple's prices are justified. but icloud storage with ppl having backup enabled by default ist just one giant rip-off.
Apple did create a nice little automatic revenue generator. It forces you to pay apple, disabled backups (with scary delete messages), or trying to navigate the backup interface to cull things to stay withing the 5 gb limit.