Is there such a thing as having too many backup ad networks? What's a good amount of backup ad networks to utilize?
Really depends. If they start to slow your servers down then I'd say take off the synchronous tags that require extensive loading. Techcrunch for example probably loads over 50+ tags (with half of them being ad networks) so think they are really trying to up their fill rate.
I only utilize three ad banners on my site at a time. I'm actually talking about having ad networks as backups to my main one.
The number of backups you should use really depends on the traffic. Generally though, 3 to 5 back ups MAX is more than enough. Find networks which are hot with Tier 1 Geo's, Then find another for Tier 2, and find another which focuses on Tier 3 and all others and target the traffic to each tiered back up, followed by a 100% Fill Base. Thats the winning strategy.
Adversal and Adsense are both 100% fill rate, I believe. Tribal Fusion is a great starter. I'm trying to find that awesome secondary one right now (Fidelity Media is in the lead).
Well what I would do is, run a report by Country, see which ones perform best on average over time for each network, then assign those countries to the network that pays most on average for it.
I'm actually in the process of doing that now. I just learned last week that my ad networks have those stats available. It's a bit eye opening.
I just found her randomly online. Figured it would make people want to help me out a bit more as I learn this marketing game.