There's not really enough value in this to make cities need to install them everywhere, but it's one of those ideas that at least makes me pause to think about it.
Pop-Up is a set of platforms that is embedded in the sidewalk and can be pumped up or down by anyone. The advantage is in being able to free up sidewalk space when not in use, while also not requiring other storage space for bulky furniture. Also, since each component can be raised or lowered independently the furniture can be used as benches, tables, or some combination.
A) Potentially filthy (dog-doo smears on your table?)
B) Some kid decides to pump your seat up or down while you're sitting on it and you have to chase him away.
Maybe you have to be in Holland for this to work.