The New Republic today looks into the Mormon practice of baptizing dead people, and the church's related efforts to preserve genealogical information:
“The core concept of why this church cares so much about genealogy stems back to the notion that families can be eternal organizations past death,” [Jay] Verkler, [CEO of Family Search, the Mormon organization that manages the vault's records and promotes genealogy throughout the world], explained. “Members of the church seek out their ancestors because we think we have a duty to them to help them understand this gospel that we understand, and we think we can actually be together.”
The church’s most ambitious project is its online tree. Anyone who logs in to Family Search may record and research his or her family history there, but what distinguishes this tree from all the other online services is that the church is trying to connect all the branches, using its massive records and the activities of users to build a big tree of all of humanity. The endeavor must be, to some extent, possible. If anyone has the records to create this structure—a family history of all of the documented individual members of the human race, this group does. But the distinctive element of the LDS tree is that it’s collaborative: People can log on and add names and link them to documents and write personal stories—and once they have done that, their fifth cousin once removed may also jump online and edit that information, changing a relative’s name, linking it to other documents, or deleting the story altogether. No one I spoke to at Family Search seemed to think this would be a problem, but surely everyone’s version of her own family is different from that of her cousins?
In the religion I'll someday build a church around—The Church of Latter-Day Atheists—people will be able to make a record of their ancestors and note that the ancestors truly don't care about the living, for the simple reason that the dead don't have anything to care with. But hey, if the Mormon church wants to spend tens of millions on building a complete genealogical database, mazel tov. A few centuries from now either everyone alive today will be Mormon or no one will. I'm not sure how either side of that divide will prove it, though.