"Most users" blindly type the same password into Facebook that they do for Twitter, LinkedIn, Gmail, OK Cupid, eBay and PayPal. Any of those services can (and do) get hacked and the password opens all the other services. Should we shut them down too?
I can't say if people's understanding of how junk food is bad for them is greater than their understanding of internet security, but I wouldn't say that they're fundamentally different things.
My point is that "what people understand" is not universal, and is highly subjective. We can't assume that everybody understand why alcohol, smoking, junk food, lack of physical activity, medecine, etc. are potentially "bad" for them. Yet, we don't ban most of these things "in case some people don't understand"?
We teach people about health and nutrition, why shouldn't we do the same about IT (I mean, it's such a huge part of our lives now that we can't ignore it)?
Too many people jump on the "prohibition" train, when it's rarely the best solution. Rather than limit what companies can do (it's rarely objectively bad, they're offering users a feature in exchange for a subjective downside. I would focus on teaching people, not limit what can be done.
But maybe that's just me.