Google minifies HTML on basically all its properties. It's probably about a 50% savings in bytes, which translates to (on my Comcast connection) about 250ms in network latency saved. Multiply out by rough estimates on queries/day and it saves a human lifetime every 2 days.

Repeated experiments - by Google, Amazon, and many smaller websites - have shown that lower latency directly translates to higher conversion rates, so I wouldn't be surprised if this results in billions of dollars of extra commerce, and even a small website would get noticeably higher revenue if they did this. Google also ranks faster websites higher, and so you get an SEO benefit as well.