2D view keeps many copies of the same object after Display()-Erase()-Display() combinations.

When you call object's Display() in 2d view it's added to the internal sequence.
After you call object's Erase() it's not removed from the sequence but gets flag
"not displayed".
After you call object's Display() once again it gets flag "displayed" and
becomes added to the sequence one more time.

Thus, you can get a huge sequence of objects just displaying and erasing one of
them.