These were popularly known as "walled gardens," a metaphor for their being nice places to visit but with limited territory to explore. Beyond the walls lay the Internet, a vaster but far less organized region of cyberspace.
An interesting article by Justin Peters that I read just today (yes, still catching up on a two-month-old issue of CJR, even though the newer one came in the mail yesterday) says that today's mega-social-media sites -- Facebook, notably -- are trying to become like those original walled-off places.
Peters, however, has a different metaphor that struck me as particularly apt. Facebook, he wrote,
"offered people the cruise-ship version of the Internet—a slick, brightly colored destination for social activities and bonhomie, safely apart from the unfamiliar surrounding waters, a service-oriented environment where you can lean back and enjoy the attentions of your very own information valet. You could leave the ship, but there’s no need to—friends, information, activities, they’re all already there, and if they’re not they’ll be there soon.
"A few caveats apply. You can’t steer the ship. You can’t see how it works. You can’t suggest destinations or routes, and you’re not likely to cruise beyond your comfort zone. You can’t easily meet people who aren’t already like you. If something goes wrong, you’re not allowed to fix it; if you’re displeased with the service, nobody will listen to your complaint."
The problem with this, Peters notes, is that these destination sites seek for people to come to them, and stay with them almost exclusively, as the central feature of their online lives. They endeavor to keep the rest of the Internet -- the part where they can't make any money by collecting user data to be monetized -- outside the realm of user experience.
It's worth a read.