Digg, Reddit, Newswire, Mixx and the like are the news and Intertainment (Get it? It's entertainment on the Internet) equivalent of Wikipedia. Like the online encyclopedia content is largely managed by the populations that use them. I don't have a problem using Wikipedia for background information or as a starting point. I do have little interest with these collective news sites. Most of them are a mess and amount to little more than popularity contests. Vote for a news story indeed. Why would I want my content managed by the whims of others even more distracted than I am? Post my own story? Blog about my reading? Allow others to track it? Time wasters all. I certainly see some marginal benefit in the ability to share what's important to me and see what others are interested in. It's fun to explore for a few minutes, but I don't want to live my life that way and I certainly wouldn't design an entire site around it.
The argument for social sites such as these is that it puts the power in the hands of the people and promotes sharing of information. And to a certain extent it does. But it is largely trivial and inconsequential activity, no better than the old model of "someone out there" providing content. What I'm interested in is a system that allows me to pick sites and topics that I'M interested in and then be able to access that info in a convenient manner. de.lic.ious is a step in that direction. If I want to blog about it and send my thoughts out into the vast Internet ocean I can do that too. Maybe someone would even read it.
Of the four social news sites Newsvine was the most usable to me, mostly because its interface was less chaotic. I can't see using any of them professionally or personally, except on a lark or perhaps to search for some unusual topic. They are all productivity wasters. The underlying framework, namely social-sharing and wikis, could be utilized in a library environment. A more specific focus would help.