also kind of unusual that this blog post is by the president of MaxCDN.
It makes a lot of sense for the president of MaxCDN to make a blog post like this. Bob the developer decides to learn about how CDN's work and happens upon this blog post. Cool, Bob just built his own mini CDN network for fun. Now Bob understands that his CDN, though a fun weekend project, is definitely not production ready. What does Bob do when he needs a CDN he can put into production? He goes to the guys that established themselves as authorities on the topic: MaxCDN.
Content Marketing 101: http://www.kalzumeus.com/2012/02/09/why-i-dont-host-my-own-b...
If you build a smallish network of, say, 10 of the $10/mo, 2-TB-traffic DO servers, and can manage to spread the load such that you use an average of half of the free allocation, you pay $100/mo for 10 TB. Cloudfront would charge you $1200/mo for that data transfer. Obviously it's not the same level of reliability or ease of scaling, but it's cheaper enough to be vaguely intriguing—$1200/yr versus $14k/yr is non-peanuts!
Afterall, what is the difference between serving assets out of your webserver
Their current policy FAQ says they do not even explicitly forbid Tor exit nodes, although there is a stern warning, so why would they disallow a proxy configuration dedicated solely to your site?