Admin Chooter, aka "Victoria" has been let go from Reddit, IAMA goes private as a result.

https://www.reddit.com/r/IAmA

Victoria did all of the high profile AMAs, and is considered the reason many of them are great and generally make sense since celebrities don't know how to use Reddit.

Chooter no longer has an [A] by their username anymore, basically showing that they are no longer and admin.

https://www.reddit.com/user/chooter

Edit:

r/Science just went Dark: https://www.reddit.com/r/Drama/comments/3bwym1/rscience_has_just_gone_private_citing_an/