Could you build a giant like youtube?

I think to come up with something big like Youtube, one has to think of something new because people usually likes to involved themselves into something new.

I have no idea where to start to build something like that. I do not know enough to do it.

Well no you couldn't make something giant that is like Youtube because that train has already left the station their are other youtube like sites that don't have the popularity and won't get that popular because Youtube was first to market and got its name out their quickly. I mean their is revision3 which is about the closest you will get to a youtube alternative. If you mean as in popularity then yeah you could make something like Youtube in popularity but this takes a lot of skill and having the idea and the know how of how you get the idea to a workable product or service that people want to use is a completely different story and that is just the big thing you have to get it to being something that people didn't realized that they needed or wanted. Like the iPod or iPad.

i think it needs a lot of budget, even metacafe.com can't reach it....

Of course, it's possible however many have already built similar sites but can't beat youtube since youtube is already a pioneer in that field. However, if you meant making a great site, I guess it will just rely on how skilled the people will develop the site and most of all if their idea is really good enough to materialize into something awesome in the future and most of originality is the most important thing nowadays.