One solution to attribution is to give credit to the person whose site you found it on. Instead of "Jon Udell writes that federated wiki is like Tumblr in that..." try "Via Jon Udell, federated wiki is like Tumblr in that..." This acknowledges that you found it through Jon Udell, and gives it some authority based on Jon's curation/editing of it. It points people to the version you are responding to as well. But it avoids claiming Jon as the author or the direct asserter of the statement. Via asserts only that Jon has published this and found it of note.
Via attribution creates a good incentive structure for curation. curators are incentivized to share things they believe to be of value, and rewarded for bringing new ideas into communities. In turn, this works out well for authors as well, as their work travels further.
If this seems odd, consider the fact that you are much like to refer on Twitter to "the article that Maha shared" than to refer to the article by the name of the author.