In theory — in practise I've had to limit Google on two large sites at work. I currently have them limited to 10/s for non-cached requests.
I have had odd bot behavior from some major crawlers, but never from Google. I wonder if there is a correlation to usefulness of content, or if certain sites get stuck in a software bug (or some other strange behavior).
But as with any contact with these large companies, our contact eventually disappeared.