I seriously believe that if done properly, a huge website can bring nearly every service together.
Yahoo has yet to accomplish this because they act on the “Set it and forget it” method, in which they build a service up using a dedicated team, and never really approve upon it because it seems to work good enough.
Take Yahoo! Auctions, for example. One could make the accusation that they closed their doors because of eBay, but I believe that it is because of the quality of their product. The style that was used felt like nothing has been updated since the late nineties. If Yahoo! Auctions was given a facelift to the quality of something like Yahoo! Answers, I imagine more people would start using said service, and as such, would not have closed down.
Facebook has taken a different turn and given third-party developers the ability to create other sections of their website, as to both reduce their work load, as well as increase user activity, bringing a cleaner myspace-style profile.
Such as they say in real estate (”location, location, location”), I believe “Quality, quality, quality” is the light that our industry will discover in the near future. Whether or not we intend to catchphrase it Web 3.0, I imagine that quality will be one of the top priorities for any successful site in the near future.