I should probably clarify a couple of things about what I was trying to say about social networks as sharecropping activities.
First, I am not trying to suggest that hosted services are inherently bad - I think it's great that services like WordPress.com and Edublogs are available - and they are not sharecropping. Hosted services can be great - they let people easily post their content, and a well designed and managed hosted service doesn't infringe on a person's digital identity, nor on their ownership of the content they publish.
Applications like Facebook, where content is absorbed and ownership is stripped through the process, are sharecropping.
Second, it's not (all) about advertising. There are ads on lots of good services - they have to pay the bills for offering a free service somehow - but there's a line that has to be drawn. If a service is overly advertised, or the ads are intrusive, then it's just not cool (in my opinion, of course). Saying a service is evil because they try to make money is just wrong. As long as it's done with taste, isn't invasive, and isn't directly messing with a person's content (i.e., inserting ads in the content itself, etc...) then it's likely OK. But it's a personal thing.
The easiest way to see if something is worth contributing to is by asking the question "who benefits by my using this service?" If it's not clear, or the primary beneficiary is the service provider, then it's probably not a good place to be, and is possibly running under the sharecropping model. Actually, that's a good question to ask when dealing with anything - who benefits? why are they doing this?
Examples of 3 hosted services that are NOT sharecroppers:
- Flickr (it's free, but they benefit primarily by Pro subscriptions)
- WordPress.com (it's free, but they make their money on paid upgrades)
- Edublogs.com (it's free, but they also sell upgrades and services)