How about needing to store your video in a variety of resolutions for users on different levels of connections (or have the CPU capacity available to transcode

How about needing to store your video in a variety of resolutions for users on different levels of connections (or have the CPU capacity available to transcode live for every single simultaneous viewer)? Also, streaming video requires higher bandwidth than text/images; where you may be able to get away with a single server for text/images, you might find a CDN (with the cost & complexity it brings) is more necessary for video delivery. The client-side player isn't an out-of-the-box thing, either-- solutions like Video.js and MediaElement.js need a myriad of plugins to approach the YouTube player's functionality, and default browser players get nowhere close. But it's the smaller part of the story, imo, because at least it's just JavaScript & CSS to deliver.