Wikipedia is a great example of where donations DO work. I couldn't imagine an internet without it, and I'm happy to donate and support it.

Sadly the data suggests that for most websites donations are not a viable alternative to ads. Some numbers here: http://blog.pagefair.com/2014/introducing-pagefair-ads/

I think the challenge is that we use many different websites every day. I've probably visited sites today that I've never been to before and will never visit again. These guys are not getting a donation from me.

Maybe the future internet will consist of a small number of donation-supported sites, but wouldn't it be sad to lose all this variety?

If those sites aren't providing anything of value, what are we really losing?