That being said, I haven't heard many people complain about excessive speed (or endangering the public) when these things roar through.  They usually start by temporarily closing off all side streets, then block pedestrians from walking into the street.  Then the motorcade roars through on the cleared streets, and the whole thing moves on.  5-10 minutes is about all it takes.

Not to say that there haven't been incidents though.  There might have been one a few years ago, but I only have a vague recollection of it all.  People who live up in NW DC near the Naval Observatory might have an entirely different take on the whole thing.