Ideas for a website

Hello
I have been thinking how huge websites such as Youtube, Facebook and Myspace have been an ultra success. Is there a chance that another website, possible making an introduction this year, would be as successful as these? Or would it probably die, since the main "media" websites have already been built (ie: video sharing -youtube-, picture sharing -photobucket-, and personal sharing -myspace-).
Do you think there are still ideas that have the potential to make someone an internet millionaire?
Or is the next thing just to make niches out of the already big websites (such as a "pet video sharing website, or a video game picture sharing website).
What do you think?

I think the next big thing in the U.S. will be "mobile" ... websites
based on small screen rendering for cell phones, PDA's and other
mobile devices.

The U.S. is way behind on services for these, but I think there will
be a breakthrough ... and it will be a big deal. Sites need to be made
specifically for the small screen, compact, viewable, navigatible,
and rendering properly for the Opera browsers or whatever will be the
preferred cell phone browser.

I'm not sure what the next big social networking site will be, but I'm
thinking it will be related to a person's location VS event (like parties,
shows, etc).

For ideas on how to script web pages for the small screen, see Flickr's mobile page.
View their HTML, CSS, etc. Notice the XHTML Doc Types, Content-Type, etc.
http://m.flickr.com/

That's my 2 cents on this topic.

Well there will always be another 'YouTube' in my opinion. Thinking outside of the box is good, but I'm just not really interested in trying to come up with that concept.

These sites all started by finding a niche, and then blowing it up into an international scale. Honestly nichés are the best way for sites to survive, because once they have captured that niché they are ready to move forward with funding and with a footing required to launch into nearly every internet user's life.

I think its also likely that one of the next big things is already here, http://www.backtype.com/ which is a method of connecting commenting systems across the web. This way you have a more uniformed presence online, which is where we are moving. I even remember reading something about a system that pulled together major social networks into a single place, or something like that.