It's interesting that he didn't include the Financial District. I know of a number of startups there, including some YC startups. He did make this a couple years ago though, and it may be that that's a more recent expansion as it's gotten harder to find reasonable options in SOMA.

I worked at Cloudera's office in FiDi over the summer and liked the area a lot. Super-convenient via BART (less convenient than SOMA via Caltrain, but one could always transfer to BART at Millbrae). Right in the middle of everything. Good food options. Felt pretty safe walking to BART after dark because there's enough people around.