The "MyGov" idea is not completely new, so let's not reinvent the good parts if they already exist. That means looking at the existing, similar platforms (in govt. and elsewhere) to see what aspects are working and what is lacking.
For example: There is a platform called "USAjobs.gov" that is operated by the U.S. Office of Personnel Management (OPM) that provides a personalized email-alerts to individuals who want receive new announcements about specific types of federal jobs. This has been around for at least ten years, so what "lessons-learned" can OPM share with us in developing "MyGov"?
BTW: I brought this up when I first suggested "MyGov.gov" to the White House on its OpenGov.Ideascale (three years ago): http://ustransparency.blogspot.com/2009/05/my-four-ideas-at-white-housegovopen.html#mygov