The #YouTube interface is particularly bad. It's optimized to keep me watching ads - which, fine. Whatever. But there's not a good tagging system, no way to share things within the platform with friends. No way to see what my friends might have liked. No integration with a social network period.
There is so much good interesting nerdy content in there, and that makes it the only good video platform I know of, but it's so bad at connecting me with it.