Working on social software, I've been thinking about the dynamics around walled gardens recently. There is a strong tendency for Web applications that benefit from network effects to metamorphosize into walled gardens. Unfortunately, I haven't found a definition of "walled garden" that I like. Most references to "walled gardens" in the context of internet services refers to ISPs creating their own closed network which is "pay to play" for publishers as opposed to giving their users access to the World Wide Web.  The most popular examples of this are AOL of old and most recently mobile phone carriers. However this definition doesn't really capture the new way in which users are being tied to a particular vendors vision of the Web, thanks to the power of network effects.

In his post Facebook vs. AOL, redux Jason Kottke writes

I wanted to clarify my comments about Facebook's similarities to AOL. I don't think Facebook is a bad company or that they won't be successful; they seem like smart passionate people who genuinely care about making a great space for their users.1 It's just that I, unlike many other people, don't think that Facebook and Facebook Platform are the future of the web. The platform is great for Facebook, but it's a step sideways or even backwards (towards an AOL-style service) for the web.

Think of it this way. Facebook is an intranet for you and your friends that just happens to be accessible without a VPN. If you're not a Facebook user, you can't do anything with the site...nearly everything published by their users is private. Google doesn't index any user-created information on Facebook.2
...Compare this with MySpace or Flickr or YouTube. Much of the information generated on these sites is publicly available. The pages are indexed by search engines. You don't have to be a user to participate
Everything you can do on Facebook with ease is possible using a loose coalition of blogging software, IM clients, email, Twitter, Flickr, Google Reader, etc.

In his post Avoiding Walled Gardens on the Internet Jeff Atwood writes

I occasionally get requests to join private social networking sites, like LinkedIn or Facebook. I always politely decline. I understand the appeal of private social networking, and I mean no disrespect to the people who send invites. But it's just not for me.

I feel very strongly that we already have the world's best public social networking tool right in front of us: it's called the internet. Public services on the web, such as blogs, twitter, flickr, and so forth, are what we should invest our time in. And because it's public, we can leverage the immense power of internet search to tie it all-- and each other-- together.

In comparison, adding content to a private, walled garden on the internet smacks of the old-world America Online ideology:

Jason and Jeff are both smart guys but they think like geeks. To me it seems pretty obvious why the average person would want to to use one application for managing photos, blogging, IM, reading feeds with updates from their friends, etc instead if using half a dozen products. Especially if the one product fosters a sense of community better than any of the other individual products does on its own. Of course, I've said this all before in my post Why Facebook is Bigger than Blogging so I won't repeat myself here.

What I do find interesting is trying to define what makes Facebook a "walled garden". Jeff and Jason seems to think it primarily hinges on the content produced on the site being visible to search engines. This belief seems fairly widespread since I've also seen mentions of it on blog posts by Steve Rubel and danah boyd. This definition doesn't sit right with me. I actually think it's a good thing that the drunk frat party pics, emotional public break ups and experimentation with new ideas that make up the average high schooler or college students life (i.e. the primary demographic of social networks) shouldn't out there for search engines to index, cache and then keep around forever. From the perspective of Jeff and Jason it seems the problem with walled gardens is that people outside the garden can't see it's beauty, from my perspective the problem is that they surround their users with beauty to disguise the fact that they are trapped (or should I say locked in?). Thus I actually think of "walled gardens" as services that limit users. This is the difference between being able to send email to anyone on the internet and only being able to send mail to send email to people who use the same ISP. It's the difference between being able to send instant messages to anyone who uses an IM client instead of just to people who use the same IM service or use a product that has "paid to play" in your IM network. It's the difference between being able to accept any payment on your online auction (e.g. Google Checkout) and being told you can only use that provided by the the owner of the marketplace (e.g. Paypal). 

When you look at things from that perspective, there are more walled gardens on the Web than people would care to admit. Why this is the case is eloquently explained in this comment by leoc on reddit which is excerpted below

Certainly it's not simple, but that's why it would be the "next Web" rather than what we have now. It seems there are two big forces creating the Web 2.0 social-site bottleneck.

One is the fact that hosting is fiddly and expensive. It's certainly better than it was, but it's still the preserve of nerds and professionals. (El-cheapo PHP4 hosting is almost cheap enough but too fiddly and much too limited; virtual hosting and up is flexible but much too fiddly and expensive.) We need a future where the casual user can drag-n-drop fairly arbitrary programs and documents into his own webspace without having to worry too much about configurations or Digg-storms or bandwidth fees.

The other is that centrally-controlled databases are the low-hanging fruit; it's much harder to create decentralised systems that work. It's much easier for Amazon to have users log in and enter their book reviews in Amazon's database than it would be for you to find and aggregate all the reviews for a given book from the Web, then reputation/spam-filter them and present them in some kind of coherent framework. (And that's assuming that people would rather put reviews in their own webspace rather than just typing into an Amazon textarea - problem one again.) Similarly, the classic wiki model is inherently centralised

In today's world, it is far easier and cheaper for the average Web user to use a centralized hosted service than utilize a service on their own Web space even if they can get the software for free. In addition, a lot of software on the Web especially social software applications benefit from network effects so once a service hits a certain critical mass, displacing it is a losing proposition whether it is an online auction market or the #1 instant messaging application. When you put these things together you get a world where the dominant software in certain categories tends towards a monopoly or at the very least conforms to a Power law distribution

And once a product gets to that point, it is easy to think in terms of preserving marketshare as opposed to giving users choice. At that point, another walled garden has been created.