Pretty much, but integrated into the browser itself, so you have a layer of interaction on top of the Web content itself (bookmark sharing, comments, recommendations, etc).
Just another Yahoo-like site has the problem that the moment you click a link you are leaving the site, which makes it impossible or at least extremely cumbersome to have features that span multiple sites. Youtube in contrast knows what you are looking at and is keeping track of it to fine tune recommendations, offer comment sections, subscriptions and such, that's not something you can do just by recreating Yahoo.
Just another Yahoo-like site has the problem that the moment you click a link you are leaving the site, which makes it impossible or at least extremely cumbersome to have features that span multiple sites. Youtube in contrast knows what you are looking at and is keeping track of it to fine tune recommendations, offer comment sections, subscriptions and such, that's not something you can do just by recreating Yahoo.