A surprising number of sites use CloudFlare. The trouble with CloudFlare is, if you want to stay anonymous on the internet using Tor, you're SOL, as they serve you captchas every 3 pages when they see a connection coming from a Tor exit node.
So essentially, if you're a Tor user, CloudFlare:
- Renders a sizeable portion of the internet unusuable for you
- Makes money on your back by making you solve captcha, and turning you into a human OCR.
CloudFlare and Google (which also serve captchas to Tor users, only fewer exit nodes are concerned) are quickly making Tor unusable, which must make the NSA wet their pants.