Here are some great articles you can read that address the problem of homelessness and lack of resources for the homeless in San Francisco:
SF Weekly: Occupied: San Francisco: Understanding the City Through its Toilets.
The Bold Italic: San Francisco's Poop Problem is Serious
The SF Chronicle: A Decade of Homelessness: Thousands in SF remain in Crisis
And please consider donating to lava mae, a service that provides mobile showers and toilets to the homeless.