[graue]

> the difference is that back then much fewer people were aware that internet exists

That's pretty much the point. In the time that Facebook got big, hundreds of millions of people were beginning to use the internet to socialize for the first time. They didn't have to unlearn how Friendfeed worked, or abandon their contacts on Myspace, because they had never used these services. It was all new and Facebook snapped them up.

There aren't hundreds of millions more for the next social network to snap up. In the developed world, the internet is done growing. Every North American or European who is ever going to use the internet already does. Everyone who would be interested in using a social network is already on Facebook.

Not literally everyone (we all know a few people who aren't on Facebook), but close enough that the trick they pulled off can't be repeated.