"Why can't the city pull a Robin Hood and take more from the tech cos?"
Now I can understand why Silicon Valley wants to secede from the rest of California.
What could justify this theft? Hipster brogrammers with goatee beards may be very annoying, but that's not a valid excuse to steal from them. There is no externality to tax. The Google and Facebook buses are reducing an externality - car traffic. So the justification must be spite and envy.
"...Because it is restricted by Proposition 218 – a Kafkaesque bit of regulation that prohibits local governments from making more money off a property-related fee than the cost of providing the item the fee is being charged against – in this case a fraction of the time available at public bus stops."
In other words, San Franciscans already have protection against greedy government officials enacting their spite-driven punitive money grabs. There is nothing Kafka-esque about this, any more than Miranda rights or detention limits are "Kafka-esque".
Yes, the State of California does need to sort out its property taxes. But the city of SF more than makes up for it:
"San Francisco property tax take to exceed $2 billion for first time "