I do think the "tech buses" in San Francisco should be paying an appropriate impact fee if they're going to be using public bus stops, but the alternative to the buses is, you know, many many more road clogging cars. Basically the Bay Area just needs more housing, especially where there are decent transportation options.
Aside from poorer people being priced out generally, the big issue is that they increasingly get priced out of the areas which have transit options. So rents go up and they need to have a car. Big tech companies moving their jobs to San Francisco would probably make this worse, not better.
This will be an issue in Philly at some point, if its slow but steady gentrification continues. I don't worry about poor people being driven out of the city anytime soon, but I do worry that the neighborhoods with better public transit (high frequency bus routes, trolleys, subway) might, eventually, become unaffordable.