[Building Sakai] User preferences changing tracking?

[Joshua Swink]

We seem to have a trickle of reports and complaints of users who can't
access a particular site, and it turns out that the site is hidden in
their preferences. It may be that all of these reports come from
people who hid the sites themselves and then forgot about it, but the
frequency of this makes me wonder.

Are there any known bugs that would make sites become spontaneously
hidden in user preferences?

Is there a way to track user preference changes, e.g. by whom and at what time?

Josh