Why YouTube buffers: The secret deals that make and break online video
While it may be true that there are some outstanding ISP issues that lead to slow internet, I think the more pressing issue is the behaviour of the new(ish) youtube player acting erratic. For instance, you cannot fully load a video anymore, it will only load a portion as you continue watching. If you wish to rewind the video, for some reason youtube will want you to rebuffer the entire from where you have rewinded to. This is terrible when dealing with slow connections. I have found that since youtube has implemented three specific things, 1) new player, 2) changing of related videos, 3) google account requirements, the user experience has gone way down hill.