Why does it retain the ability to replay their actions years after the fact? And why do "removed" videos not go away?

It depends on what kind of 'removed' video they are talking about. If the video is taken down
due to a "take-down" notice from a copyright holder, you get a subpoena which says you have to
keep and store that data. In that case, every copy of the Family Guy that has been taken down
has to be stored until some date in the future. There is also the fact that other data may not
be deleted because they want to do research on it in the future.

Google is a vast money making enterprise because it does constant data research. To do that
with old data, they must store everything even if they do not know what they are looking for
currently. [Of course there is the other problem that occurs in acquisitions.. group A may
store more or less than group B.. and everyone gets smeared when it comes to light].