In Berlin it is a good talking point. I am not commenting on whether it is effective or good policy, just that you can score politically with it (well, until th

In Berlin it is a good talking point. I am not commenting on whether it is effective or good policy, just that you can score politically with it (well, until the court now killed it, I suppose). Concerns about being able to afford rent not just now but in the future is a major concern for a huge chunk of the population. They look at what happens in other large cities with rent prices (be it Munich, be it Paris, be it SF) in fear. Berlin itself uses an unofficial slogan of "Arm aber Sexy" ("poor but sexy/attractive"), coined by a former Berlin major referring to the budget of the city but adopted by the population to mean the people living there as well. They fear that driving out poor people - including themselves - and turn it into yet another place for the rich, and/or fear "over-development" will destroy the character of the city (and the ecological consequences of such developments; the Green party is big in certain parts of Berlin). I can see that with my sisters, who have been living in downtown-ish Berlin for a long time while "poor" (think student, almost-unpaid intern, unemployed), and who constantly complained about the rents (that my parents and later welfare paid) and scarcity of available apartments, but at the same time were e.g. very much against any plans to develop the large area of the old closed Tempelhof airport, where all plans to develop that area were abandoned after multiple public referendums decided that the area has to remain a "park". That alone is 12km² of now entirely unused space close to the heart of the city, space for about at least 50000 people considering Berlins current population density of 4118 people per km². Or develop only half of it, and leave 6km² and that's still a ton of new apartments. But nope.