OK, for most of my time as an Adsense publisher, I've never really used the Backup Ads option for anything but showing blank space as a form of backup ad when creating new ad units. To this day, I can't ever remember seeing a blank space because no ad was available. I'm discounting times when the ad script hangs and nothing shows up.
So, does anyone have evidence that Google ever shows a backup ad? My personal experience suggests that there is always some piece of junk to throw in the ad slot, even if it's completely unrelated to the content on the page and has nothing to do with the visitor's interests. Is this why people report irrelevant ads so often and is showing irrelevant ads just a way to make sure no other ad service gets a shot at the slot? Inquiring minds want to know. ;)
Hmmm. Subtitle should say "blanket" not "blanked" so you can tell I was thinking about blank spots when I wrote it. Or I'm a lousy typist. Take your pick.
I usually use one of my own ads (or at least my own graphic) so that I can tell if and when Google doesn't show an ad. Doesn't happen often, but it does happen from time to time. I've also used affiliate ads, but since the strategy behind affiliate is vastly different, they don't perform. But at least I can track that they displayed.
Thanks, I've had the impression that 1. Backup ads are infrequently used and 2. They can be tracked in a variety of way.
Probably not as effective as chaining a few ad networks together via another program then.
On a side note, does anyone have any solid info on using Adsense as a default in another CPM program (say ValueClick - now ConversantMedia)? Seems like it would be a violation of the terms but I also have heard people say they do it (or have gotten away with it). Anyone have some concrete info on this?
Adsense as passback for CPM networks is allowed (afaik, source: adsense rep) but the bad performance doesn't make worth it (maybe got something to do with the fact that it has to read up the dom tree through some 10 nested iframes before it encounters any keywords to target).