Human Transit reports that the city will soon have "the most aggressive free market parking policy in the nation."
The goal is to ensure that there's always a space available, so that people stop endlessly driving in circles looking for parking. People will be able to check online to find out the current parking cost in the place they intend to visit. Parking garages will have a better chance of undercutting on-street rates, so that those garages can fill. If you've ever driven in San Francisco, you know that it's hard to decide to use a garage because, well, if you just drive around the block once more, you might get lucky. Under SF Park, if you just drive around the block once more, you'll probably find a space, but it will cost more than a garage, especially if you'll be there for a while. So drivers are more likely to fill up the garages.
If the program fails, which I hope it doesn't, it will be as a result of being too timid. There will inevitably be pressure to set a maximum parking price, at which prices will stop rising, which means that space will fill up, which means that everyone will be driving around the block again. Andrew Price at Good asks: Could parking costs reach $10/hour? Conceivably yes, for a few high-demand hours, which are almost certainly also hours when transit is abundant. What's wrong with that?