What's the use of having people's date?

[zack654]

I am beginner in Web Development and I just wonder what's the use of having people registered on your site. So, you will have theirs emails, passwords , etc. Maybe this sounds stupid for some experienced developers, but I really don't understand it. Do they make money this way somehow, or what..

[MagicMedia]

You can keep track of who's who. You can also prove to potential investors how much your site is worth. Simply put, the more people visit your site, the more valuable it is.