<insert "when you're a hammer..." joke here>

Not to be a jerk, but, running Facebook over AWS is not a CDN problem. That's crazy talk. There are far more Facebook requirements that AWS can meet that Akamai cannot. You have to look beyond their content delivery reqs.

Also, they could absolutely have 800k servers. I don't think comparing their size to Akamai is fair. The requirements of each company are drastically different.

Do I think the 830k is accurate? No, but only because these estimates are usually wrong (unless informed by an inside source).