I agree that it is unlikely that the majority of miners have configured backup pools at all. And I question if that is a problem.
Most miners probably monitor their machines regularly and can and will switch to other pools manually within a couple of hours, if the need arises. Taking a risk of a few hours downtime is not that big of a deal for small-time miners. Is it probably not even worth the time to configure backup pools.
Ah, I disagree. First, I would think most miners have some basic technical chops or they (A) wouldn't know about Bitcoin, and (B) never be able to figure out how to set up a mining rig.
I agree that a lot of people probably mine without backups at first, but the first time they notice they've not been mining for a few hours, they'll figure out they can setup backups. Even small time miners, any downtime is a big deal. If you're only making 1 BTC a month, every .01 BTC is important.