Ask HN: At what point did you hire 'ops'?

I have always worked at Megacorps, who are constantly trying to get the op:server ratio smaller. The yardstick management often use is a large scale web company (which is far from apples to apples, but I won't get into that here). But after catching a recent architecture session from a startup who only had ~100 servers I am curious about how many servers per op the average web company has?

For clarity, the persons primary function should be everything below the app layer, but that obviously doesn't exclude people who may also contribute code to the app (ie devops).

Also interested to hear of you are into the 100's of servers and have yet to hire anyone who fits that description.