Another second-order effect of rent control is increased traffic. Suppose you have two residents with significantly below-market-rate housing at the same quality level, one in downtown SF and another in Mountain View. The former starts a new job at Google in Mountain View, the latter starts a new job at a trendy start-up in downtown SF. Since they're paying significantly below market rate, they're unable to trade apartments with each other without paying a significant amount of money.
So, because you cannot trade apartments without spending significantly more money, there's a couple of hour-long commutes instead. This is part of a general pattern - messing with prices doesn't help, since the market still has to clear. You just start paying in things other than money. Paying for things with money is great in general, since then someone else has the money. Paying for things with a longer commute is terrible, since there's no beneficiary.
So, because you cannot trade apartments without spending significantly more money, there's a couple of hour-long commutes instead. This is part of a general pattern - messing with prices doesn't help, since the market still has to clear. You just start paying in things other than money. Paying for things with money is great in general, since then someone else has the money. Paying for things with a longer commute is terrible, since there's no beneficiary.