Consider:
- donations to climate deniers such as CEI
- work on totalitarian tools such as project dragonfly or PRISM
- sabotage of competitors, e.g. breaking search and YouTube on Firefox
- feigning investment to steal ideas
Of course, in big companies, bad stuff is bound to happen every now and then. I just think that the above can't be explained away as isolated mishaps, because it happened (or is still happening) over long periods of time, involving many people (quite a few of which resigned as a consequence).
Similar criticism can obviously be leveled at the other big players, and I wouldn't work for, say, Facebook either.
On the other hand, I wouldn't expect, say, Microsoft, to develop a dystopian search engine for an authoritarian regime.
Surely, most people who are working at Google do so without contributing to any sinister purpose (unless you consider ads evil I guess). I just feel there are other companies with considerable impact where I wouldn't have to worry as much about potential abuse of what I'm building.