I wouldn't worry too much.

Drawing in CSS like this isn't as simple as dropping jQuery on the page.

If there was a jQuery plugin to automate this process from image to css, then we should worry!

How so?

I think more than "you'll break the web" the issue is that it's almost never the right choice to make when compared to using more traditional techniques (e.g. images or svgs). Also it won't work in older browsers.

Just try visiting the page on iPad and zoom. You'll know.

(Hint: browser crash)

Browser crash?

Better fire up IDA!

Zoomed just fine on my ipad