[MrWonderful]

Yes, it actually is, I use it for a simple website I use. It actually decreases the load on it. But, you lack a lot of features and you can increase it. It cost like $20 or more per month up into $100 per month it depends I think. But, they probably don't want to go this route.

https://www.cloudflare.com/plans/

[atmosx]

I'm sure CloudFlare's free plan doesn't target websites with the amount of traffic wikipedia has.

Come to think of it, it is interesting that they server all this traffic using Varnish + HHVM/3.3.0.