I suspect all Google employees already have good enough health care to get a free flu shot for their family without this, he's making sure all others do too?
The flu makes society horribly unproductive (and cranky) so it's a public good.
It would be nice if he's just being magnanimous, but I actually hope it's an experiment ... will there be a notable difference in flu rates in the area as a result of this? will there be any other statistical blips that can be correlated to fewer infections? I'm hoping they're tracking the heck out of this effort :P
It probably won't even show up. There have been some unintentional experiments with the flu vaccine, such as the year production got botched or that the people in charge of predicting which strains to include guessed wrong. There were no noticeable increases in sickness or morbidity in those years.
Don't take this too far; the data is very noisy and maybe it was there and we just didn't see it. Flu vaccines do seem to work in labs and in small community experiments.
Nevertheless a nice gesture - though there may be more effective ways to spend the $$$ on the public good.