Recent moves by flickr.com to restrict access of their users in some countries (among them Germany, Singapore, Korea, Hongkong) have revitalized proposals to separate the "social network" aspect of web 2.0 applications (photo and video sharing etc) from the "hosting aspect", so that users will no longer lose their social network when changing a hosting provider.

Depending on the legislation under which a person lives, the definition of what is legal or illegal does vary quite a bit and there is obviously no easy way to respect both the demands for liberty of expression and for safety from legal prosecution if a network crosses national borders. Chances that this will change in the foreseeable future are almost zero.

That's why I'm trying to think of a different approach: Let everybody be responsible for their actions and the content they are posting also in a strictly legal sense.

What requirements would a web 2.0 system have to meet to support this principle? Just a draft proposal:

1. Legal issues to be considered
IANAL, but as far as I understand mainstream internet legislation, the owner of a site / domain name can be held responsible for forum content posted by a third party on his/her site. And as far as I understand common TOS of most web 2.0 hosting providers they try to shift that burden to the users (users accept they will "indemnify" the hosting company if trouble starts ...).
From a legal point of view, posting links to doubtful content is already a risk, while search engines so far need not check their content, the only thing they need to do is to remove a search result leading to illegal content on request.

2. Basic function: content posting
The system should allow photographers/artists to post their photos/videos/artwork on a hosting platform of their choice, for example on their own websites with own domain name, on a free webhosting site, on a specialised free or paid photo hosting site (with easy to use uploading/tagging interface) etc.
This would give you some choice regarding legal aspects (chose to have the content hosted in the country where you think it will cause you the least possible legal trouble).
Plus it would give every artist a free commercial choice (bandwith vs. cost/advertising) for commercial aspects of hosting.

3. Basic function: commenting / faveing
People who like to comment or fave should be allowed do so on their own space, so they would have a clear responsibility for what they are posting. 
Following this approach a photo/video artist can't be held responsible for abusive, violent, embarrasing, indecent or otherwise objective commenting by a third party.
The risk of linking to doubtful content would be with the commenter, however. To exclude the risk that a photographer posts a nice picture, collects lots of favorable comments ("great stuff" etc) and faves, and then replaces this photo/video by offensive content, some sort of time-stamp mechanism would have to make sure that this sort of manipulation gets detected and comments/faves don't automatically link to the new photo/video unless the commenter explicitly choses to comment on the new photo/video. Maybe the most difficult thing to implement from a technical point of view (if you want to make it hacker-proof).

4. Linking original posts and comments:
Some sort of "search engine" (at least in the legal context search engines are operated) should fulfill the task of "collecting" comments linking to a photo/video. The system might be somewhat similar to the "what links to site xy?"-function some search engines provide. And if every comment can be identified by a permalink, answering to a previous comment instead of the original post would be possible.
Btw. this would be a little innovation compared to classical linear threads: tree structured threads would become possible (also more tricky to implement an easy to use user interface for this, however).

5. Practical restrictions
As some other folks have pointed out, the database size needed for the part of the job I would assign to the "search engine" is certainly not neglectable. And that might be a problem for a non-profit organization running it.
To restrict the database size needed for the "search engine", users would have to "submit" both their original posts (photos/videos/blog posts etc) to the search engine and their comments. But once you've chosen to participate and have set up your account, this could just be a background function "triggered" by clicking the "post this" button on the user interface to this service. Comments would be visible on request only (technically speaking), but of course the software could be made in a way every user can decide whether the software fetches comments by default or on explicit request from the "search engine".
This software could either run on your individual computer (as a plugin to your web browser or as an independent application), or on your webserver using standard methods to cooperate with any web browser.

6. Self-determined filtering
While the hosting could be handled in a commercial way, the search engine would have to be non-commercial and special care should be taken to make the design "censorship" free, while providing some options for self-determined filtering. For example I might want to see only photos with my children, my grandma ;-) or at the office that originate from contacts I know as "safe". Or I might like to restrict my "search" to photos from my family, etc. And I might want to block content from my view originating from artists I consider to be offensive or just boring according to my personal tastes.
And I should be able to block commenting my work by persons I don't want to do so. Of course everybody must be free to comment and link to my work on his/her own space. But I'd like to reserve some sort of "copyright" as to who is able to "use/modify" my content by posting comments that will turn up in a search for "who is linking to my content". Might help as a measure against notorious trolls, too.

6. Groups
Groups might be implemented based on a simple initial post stating the idea of the group, giving the possibility to post own photos/videos/comments linking to this initial post. Same basic mechanism, maybe it would be nice to have some tag that it's a "group" to be able to provide a nice user interface. And as large groups on services like flickr.com show, substructures in groups will soon become a feature people might ask for. As discussions on "abuse of administrative power" on flickr.com show, there might also be a wish for some sort of "open groups" without rules, maybe based on tags nobody can "own" or "control".

So far for today. As I said, just a draft needing much refinement. And maybe a little utopian. But "lose your dreams and you might lose your mind" (Mick Jagger, in "Ruby Tuesday").

And please feel free to comment, I always like an honest and critical argument.