YouTube have been taking clips down for the last few weeks after a successful law suit in Japan. There is no conspiracy with the NFL having their clips removed, they are just one of the many companies that are simply enforcing copyright.
I call shenanigans. If I want to repeatedly see Will Allen decleating Steve Smith (which, as we all know, NEVER EVER gets old), there is no authorized, legitimate NFL source for that clip. The NFL isn't losing money by it being on YouTube because the NFL doesn't offer that service. What possible harm is it doing to the NFL to have those clips online?
Actually, with the NFLs renewed emphasis on the international market, you'd think they'd want to spread the word about American football as much as possible. The clips on YouTube are usually the most exciting or interesting plays. Wouldn't it be great marketing to have the NFL's greatest hits freely available for the world to see? Maybe people in other countries see it and like it and consequently start buying jerseys and demanding that NFL games be shown in their cities/countries. It seems to me like the NFL is wasting an excellent opportunity here. If I were in charge of the NFL marketing machine, I would have an authorized repository of "greatest hits" clips available on NFL.com at relatively low resolution, then I would sell hi-res versions for download and on DVD.