Yeah, but if you do this and purchase apps, they're tied only to that one Apple ID. Might be fine if you really only use free app downloads or bought ones you'd only ever use with that one iPhone? But I had 2 Apple ID's before; one for my iPhone and one for an iPad. Thought that would be a great way to keep the (mostly music related) iPad apps totally separate. But over time, I sold the iPad and found I didn't really need one anymore. And now I've got all these purchased apps kind of held hostage over on that Apple ID.
A LONG time ago, Apple hinted at eventually allowing people to transfer purchased apps from one Apple ID to another, at least as a one-time process. I really wish that would have happened.