Another issue that has come up with respect to the geni.com kerflufle is the question of "the one true tree." The debate has been framed in terms of a choice between everyone working on their own, private trees and everyone contributing to a master tree with a single "profile" for each person. There are the predictable questions of how to make trade-offs between efficiency and quality control.
Personally, I think we need to look to the third model, which I think is kind of a genealogical version of a folksonomy. For the long version of a definition, refer to this article by Clay Shirky. For a short definition...a taxonomy is when you arrange things in pre-defined, top-down categories, and the operating assumption is that there is a "right" category, or categories, for each thing. To my thinking, this is analogous to the one true tree approach to genealogy. A folksonomy, on the other hand, is a bottom-up sorting system, where each user tags things with his or her own categories, everyone can see how everyone else has tagged those things, and what is useful emerges from general consensus. Oddly enough, someone is already doing this in the genealogy world...Ancestry.com.
Consider. I can build a tree on ancestry.com. This is my tree, and only those people I specifically select can edit it. But, through Member Connect, I can tag people in other trees that I think are, or could be, the same as a person in my tree. Now, I get the efficiency of seeing what other people are doing without the rigor and angst of forcing a merging of our research. The same is true of the ability to link people in my tree to source records like census records and newspaper pages. Anyone else looking at the same census record can see this link and other records that have also been linked to the person this record has been linked to. The more people who agree with these links, the stronger the consensus, but no one is forced to accept the consensus view against their will.
Of course, if I don't want to collaborate, the ability to link source records to people in my tree serves as my own personal set of organized bookmarks into ancestry's monster site. Which is also sweet.