According to the info, that's all YouPorn uses CDNs for (page assets minus video). That might, or might not have changed recently.
I'd imagine that paying extra for shaving a few 10s of milliseconds off latency might not really be much of a benefit in this type of a business, they are not doing VoIP phone calls. I'd imagine having fat pipes on a decent tier is #1 here.
The point of using a CDN (in this case) is not to reduce latency. The problem is that it becomes exponentially more expensive to serve high data rates out of a single data center. Basic infrastructure like switches and loadbalancers start to get crazy expensive, as do their support contracts. Also, it requires a lot of fairly rare (and highly-paid) expertise to set it up.
Distributed CDNs are like the RAID of content serving. Each node can be simpler, cheaper.
Another bonus of using CDNs is that you're in a great negotiating position. If you're serving 80% of traffic through one and 20% through another, you can flip it around the moment one offers to shave a percent or two off the price. I've had people in the sales department of the formerly-80% side notice the traffic drop and suddenly call up with counteroffers. In contrast, getting someone to draw fiber cables across the datacenter usually requires a lot of onetime expense and long-term contracts.
I'd imagine that paying extra for shaving a few 10s of milliseconds off latency might not really be much of a benefit in this type of a business, they are not doing VoIP phone calls. I'd imagine having fat pipes on a decent tier is #1 here.