Wouldn't this (Auto updating rolodex) be something trivial to add to any other platform? On almost every forum one can always click on the username and see post

Wouldn't this (Auto updating rolodex) be something trivial to add to any other platform? On almost every forum one can always click on the username and see post history and a bio. As long as the the fields of interest are included (phone/email/etc) it would serve the same purpose. As usual its the critical mass problem but facebook has done nothing particularly technologically inovative.