Looks clear that youtube only lets in connections it can easily track.. Guess the purpose.. $$$$$ !
Doesn't have to do with Firefox, Chrome, Adobe or your cookies...
It's a question of tracking you down to see exactly what you look at.. how many times, from where, at what times, forcing re-connections... Knowing and comparing your OS, your Browser, your cookies from previous sites, ranges of time... GATHERING INFORMATION.
Using a "secure or hard to track" connection, youtube doesn't work. You'll be able to see only 1\2 a video, and no more. F*** youtube and their lack of security. BTW, this site does almost same thing. They force a Script... or sign in to let you post something... Not cool... No. Over 9000!