Instant messages introduce many of the same problems that e-mail does.
That is, they must look at all the possible trajectories and outcomes within the site. Genealogy in the Internet age is a different story. People are still waking up to the possibilities of the Web. There's a periodic lag between the amount of computing power the industry can pump into users' hands and the number of useful things the software industry can devise for us to do that actually require an investment in that kind of power. Any feature should be motivated by a user-centered design process, rather than as a way to 'add something' to the site that the competition doesn't have.