Yes, but I think the OP was referring to a very important difference. The rich in Florence were actively promoting the development of arts and culture. The rich in the Bay Area are simply collecting it. Sure, you are correct that much of it was private, but the architecture, and public buildings (and the paintings within them) were for everyone - or at least, so everyone could see how great they were. In that aspect I suppose they are similar, they both think/thought of themselves as the greatest city in the world.
But where Florence contained one of the most impressive public buildings in the entire world (the Duomo was a public building and an engineering marvel), San Francisco has comparatively weak museums compared to cities like New York, London, Paris, or even Florence. Sure 3 com park, and free concerts exist, but nearly every large city in the world has that. New York's Shakespeare in the Park, and the wealth of other free public art and music in that city is significantly more impressive. Even more importantly, as wealth has flowed into the Bay Area, the artists and culture creators of the city have simply been priced out.
That being said, the argument that software is our current society's art and that software developers are the Florentine Renaissance artists might have legs.