I recently emailed the Guardian (UK newspaper) to tell them that an element of their website caused one of my CPU cores to spike to 100% utilisation while it was in view. It happened on my laptop, work desktop and phone. If you're a visitor, it was the graphic next to the podcast banner which looked like a sound wave.

They've removed the element now and sent a very nice message saying they'd investigate.

I really think/hope that the next "big thing" in software engineering will be energy efficiency in some form or another.