How fast of a connection do I need to watch youtube videos at HD 1080 pixels?
According to most major manufactures, 10MBS seems to be what's needed, but I know people with slower connections who have no issues at all. I was forced into a copper wire connection before FIOS was installed here, and had a pathetic 3-4MBS connection...that didn't work, so the 10MBS seems a good baseline.
10mbps is the bare minimum to watching 1080 with little to no buffer. If you start downloading something else the video will stop and buffer again. It'll be safer to get something about 15mbps or so. Especially if you aren't the only one using the connection.