I really don't think this is a big deal. I run a medium size website with well over 2000 uniques users per day and also require the referer header to use the we

I really don't think this is a big deal. I run a medium size website with well over 2000 uniques users per day and also require the referer header to use the website. So far, I've yet to receive a single complaint or find a browser that doesn't send it. It might be optional as per the spec, but it's completely ubiquitous at this point, and provides an easy way to add an extra layer of safety for web developers.