It will break your page if you aren't sent a polyfill when you should have been. Imagine running a browser without Object.observe, spoofing an agent of one that

It will break your page if you aren't sent a polyfill when you should have been. Imagine running a browser without Object.observe, spoofing an agent of one that does have it, and you aren't sent it. Suddenly data-binding doesn't work at all.