While I was at Google, someone asked one of the very early Googlers (I think it was Craig Silverstein, but it may've been Jeff Dean) what was the biggest mistake in their Google career, and they said "Not using ECC memory on early servers." If you look through the source code & postmortems from that era of Google, there are all sorts of nasty hacks and system design constraints that arose from the fact that you couldn't trust the bits that your RAM gave back to you.
It saved a few bucks in a time period where Google's hardware costs were rising rapidly, but the ripple-on effects on system design cost much more than that in lost engineer time. Data integrity is one engineering constraint that should be pushed as low down in the stack as is reasonably possible, because as you get higher up the stack, the potential causes of corrupted data multiple exponentially.
It saved a few bucks in a time period where Google's hardware costs were rising rapidly, but the ripple-on effects on system design cost much more than that in lost engineer time. Data integrity is one engineering constraint that should be pushed as low down in the stack as is reasonably possible, because as you get higher up the stack, the potential causes of corrupted data multiple exponentially.