If it became possible for consumers to side-load applications, the iPhone (and iPad) would lose what is in my opinion one of its biggest positive selling points: that Apple is acting as gatekeeper for executable code.

As soon as that capability exists, my elderly parent's and elderly in-laws' iPads will quickly fill up with malware and scamware like their desktop computers routinely used to.

And before you argue that you could choose to not open that pandora's box on particular devices. But as soon as enough developers decide that getting around Apple's fees is worth the effort, use of it will become commonplace and potentially unavoidable.