I worked in central SOMA from 1995-2002. In the 90s, the most prominent neighborhood fixture was the homeless shelter at 6th and Bryant, and there most certainly were homeless around there and human poop in the alleys along 6th, it was notoriously stanky. The northeast end of SOMA wasn't as ripe, though.

Things changed after the first DotCom boom and the advent of Pac Bell Park.