First off, let me just say people who whine about bugs in betas, instead of simply acknowledging they're there and reporting them to Apple so they can fix it, are absolutely ridiculous.
But, given the fact that Apple could, if they wanted to, make it, if not impossible, very difficult for non-registered devs to install betas. But they don't. (Just as they don't even have any kind of verification process on OS X.) Also, they don't charge for iOS. This leads me to believe they don't give a flying duck about non-devs running betas, but they won't help anyone of them either if things go wrong.
But shouting about how it's illegal and all that? Please. That's as ridiculous as dissing iOS 7 for draining battery after having tried the first beta...