I very much want open social networks. I support the open social web and the Bill of Rights for Users of the Social Web. I am glad to see that claimID is leveraging OpenID to handle contacts and let me assert things about my relationships to others in an open way. I sincerely hope to see a ton of work on the Microformat push for social network portability. However, I do not expect we will see well-established (read, facebook and myspace) networks opening up any time soon, because I think they have strong incentives not to.
The value of a social networking service (SNS) is mostly in its user base. Early SNSes failed because they could not attract enough users. Current SNSes struggle for the same reason. I am on pownce, plaxo, and virb, and I like them all, but rarely do I actually log into any of them; without more of my friends, they don't prove to be very interesting (were it not for the awesome Justin Thorp, I may have forgotten I was on Pownce). Linkedin and twitter are a lot more fun because there are actually people there, and, of course, this is a big reason facebook is so attractive, and why starting at colleges was so brilliant; at a college, something that makes coordinating with (and making new) friends easier can spread like meningitis.
For me, few social networks offer particularly interesting features. They pull together a blog, your photos, your videos, and some contact features (forums and private messages), and then let you put it all together in a semi-professional-looking web site. However dedicated services like blogger, flickr, youtube, and gmail do any of the individual feature better. If all you want is the public profile to showcase your personality and interests, hosting is dirt cheap and HTML tools (from google's page builder to dreamweaver) are better than ever.
Web applications and web pages are not the big draw of a social network, though. What social networks do is help you distribute your content (blog, pictures, videos, links, etc) to other people whom you think would be interested in those things. Additionally, with your profile page, SNSes offer some projection of your self to people you know or want to know (see danah boyd's excellent "Why Youth (Heart) Social Network Sites: The Role of Networked Publics in Teenage Social Life" [PDF link] for a real discussion of this aspect). Service like virb and plaxo have realized this and get out of the way of your existing services, providing only the profile building and networking features and then aggregating your content from other dedicated web applications. Facebook has pretty well gotten out of the feature business by opening itself up as a platform, thereby letting others take care of the "what do I do not what I'm here" part.
Note that I am not trying to say that features can be ignored. If facebook didn't make hosting photos really easy and MySpace didn't make sharing music simple, they'd die off quickly. But, as long as they do an OK job providing most of what their users want, and they hold tightly all of their users' connections and existing content, users will be loath to find a service with "better" features; as adopters of new, more feature rich networks have found, it's a pain to re-invite your friends and update more than one site with your new content (hence, the whole desire for portable social networks). And, if only some of your friends come with you to the new network, even money, you'll be back on the old one sometimes. So, if your connection data are the really valuable part of the social network, why on earth would one give that data away? Well, without pressure, they won't.
For those of us desirous of portable social networks, though, I don't think things are hopeless. There is still money to be made on social networking, and the major players are not fulfilling our every need. Pownce does a great job of making sharing files and events with different groups of friends easy. Twitter has the microblogging thing down. Specialized networks, such as the ones created on ning, can be extremely useful. As long as major players don't absorb every feature that niche networks create (which facebooks apps could potentially do), people will want portability because they will want to try the new, more feature-rich SNSes. And for the smaller networks, portability is the best imaginable way to compete; although it would be unlikely that pownce or ning could grow to the size of myspace, it is not unimaginable that all of the small networks combined could equal one of the big players. And, if the smaller networks do find a standard and open up the connection graphs and content, then they can compete; if I can find niche networks that serve me better and can easily have all my friends on those networks, then I'm more likely to go with the service that offers the best features, not some catch-all service like myspace. If then the major players feel that they are losing people because they are "walled-gardens," some will open up. Others will try to replicate (or just buy) the features of the best niche players. And some will just die off. But, I don't think petitions or demands will open anything up -- our best hope is market pressure.