1. Tech buses were a response to people living in the city. I don't think not having them would necessarily "force" them to live on the peninsula. When I worked for a company in Sunnyvale that didn't have a private bus I still didn't move down there.
2. People act like this is a simple matter of getting more money into public transit. This is silly, even if that was the only roadblock (pun intended!), building a new freeway takes a lot of time, and expanding public transportation takes a lot of time, and in the meanwhile makes things even more miserable for everyone. Just look at all the very modest light rail expansions in the city and how they've made those sections nightmares for traffic for years. Google and FB need solutions today, not 5 years from now, and personally paying for shuttling their own employees seems like an incredibly environmentally conscious and fair way to handle it: don't forget, they're decreasing congestion on muni/bart/caltrain for everyone else. Lastly, money isn't the only problem: there's a lot of politics in public transport. For example, the reason the BART doesn't go all the way to Cupertino is because they voted against it there. So when you throw around expanding public transport as if its a defense of poor existing SF residents, realize that it may also be a form of antagonization for people in other communities. Hiring your own bus seems to be the simplest, cheapest, least displacing, and fairest way of solving this problem.