Huh. I don't spend too much time around SOMA, but last time I was in in the area around UW at night, it had a less pronounced but still similar vibe to Haight St in SF or parts of Telegraph in Berkeley. Various groups of people who appeared to be setting up the sleeping bags and pit bull for another night in the doorway of a closed store or restaurant.

SF is a particularly bad case, but as far as I can tell, Seattle has plenty of this too.