While this blog post has very little in the way of proof, we actually got screwed over by CF a few weeks back. Basically, one morning all requests started being slow: small responses would take 7 seconds (within a few milliseconds, if you accounted for the RTT to the edge) with 7 seconds TTFB, larger ones (not sure exactly what the threshold was, but it was hundreds of KiB, not MiB) would take 1 minute (again, almost exactly 1 minute), but these would just stream very slowly. All while having cf-cache-status: HIT.

It turned out we got throttled because we were serving some (a minority, something like 10% of the traffic) video files from the domain and they wanted us to upgrade to enterprise (from business, I think). We just stopped serving video through them.

The annoying part was that we weren't notified and, obviously, had some downtime (no way you can call a site loading in 5 minutes up). They said they have released an update that does notify customers when this happens, though.