[scythe]

SF, and the Bay as a whole, is the northernmost large snow-free area in the country. The weather alone practically guarantees someone will find a reason to live here. If there were other negatives besides high prices, I think the concern over decline could be more well-founded, but there will always be some sort of city by the Bay.

[DrScump]

  the northernmost large snow-free area

You can go a long way north of SF before you hit an area that has snow in any meaningful amount, excluding a few mountains/volcanoes.