iPhones have a nasty habit of deleting stuff when they think they need the space for something else
Erm.... can you back up that unqualified statement please. Sound like a load of FUD to me.
As far as I am aware, if an iPhone/iPod/iPad is out of storage space it is out of storage space.
Unless you're deliberately trying to store stuff in volatile storage areas such as the RAM in which case its your own fault.