Earlier quoted context omitted.
When did San Francisco become the hot property? I know that the last time I was out there, about 2005, tech was still in the valley and SF proper was relatively low rent, bad neighborhoods, and no tech presence. Does this industry (to the extent that you can call AirBNB, Uber, and Twitter the same industry) really act like a flock of grackles or starlings, descending on a place, eating everything, and moving on?
It's part of a nationwide(global?) urban renewal. Millenials and their successors are more likely to want to live in urban areas and stay single longer than their older counterparts. This is causing rents to increase noticeably in nearly every major urban area. Couple that with relatively high pay for tech sector jobs that like to hire these younger folks and you get it even worse in SF, Seattle, etc.
[1] http://fivethirtyeight.com/features/why-millennials-are-less...