More Weirdness in an Over-Loaded Google Calendar

While experimenting to see if I could delete calendar items from a calendar and thereby finally clear an over-loaded test account I got this message:

 "Oops"?  Cute.  Too bad I do not know any serious corporations that ask for cute.

The goal was to see if deleting items would get me below a threshold, or if the threshold was irreversible.

The weird thing is that once I got that message, previously-deleted objects began re-populating the calendar.  Calendar zombies had risen from the grave!

Clearly there's a cache of the deleted items.  I have no information on when, how often, or if it gets cleared in a single session.

There is also some interesting behavior with old items.  To see this, load 10-15 years worth of calendar data and then travel back to some month in the year 2000.  The following unobtrusive message will display while the data renders (and it seems to take a while):

So there's either some background mechanism shunting historical data into slower, longer-term storage, or the system is not really optimized for rendering arbitrary stretches of time.

Added on September 6, 2011:
A variation of the above: cannot load your data -- come back when it's more convenient for Google....