It'll grind the context it's running in to a halt. The point is that nobody wants their site to be broken, so they won't request that with a <script> tag.
> The point is that nobody wants their site to be broken
Nobody wants it but unless it's completely broken most don't care enough to do something about it. Which is why this JSON trick is done in the first place.
Given this is about Google: YouTube has the same bug in its comment text fields for at least 5 years, in rare cases submitting a comment only results in the error "n is undefined", it can't handle the browser's back button, sometimes links don't work until I scroll the site a bit, the new "preview video on hover" feature doesn't reliably react to mouse events and its animation swallows mouse clicks, and that's just the few things I remember off the top of my head.
