I've been running AdMob's ads on my mobile sites for a couple of years and have been very happy with both the revenue and AdMob's service and support. In the last six months though I've seen AdMob's fill rate decline from nearly 100% to about 60% with a corresponding decrease in revenue. I suspect the decline is due to the recession combined with the huge increase in the number of mobile sites and mobile web traffic that has occurred this year without a corresponding increase in advertisers.
To make up for the decline I've started using Google's AdSense for Mobile as a backup. I have code to check see if AdMob has returned an ad and if not to call AdSense. Up until Dec 21st this was working well with Google serving around 3500 ad impressions per day. Users don't seem to click on the AdSense ads as often as on AdMob's and Google pays less per click than AdMob, but a little money is better than nothing.
On December 21st Google suddenly and completely stopped delivering mobile ads to my site. The online AdSense daily reports show a cryptic "no data to report". AdSense's monthly report shows data (impressions, clicks and revenue) through the 20th but nothing after.
I've verified that AdSense ads are in fact no longer appearing on the site, only AdMob ads. If AdMob has no inventory, I should see an AdSense ad but I don't. When I temporarily removed the call to AdMob to force all requests to go to AdSense I got no ads at all.
I haven't changed the code or anything else on the site. It looks like either something broke or AdSense suspended my mobile site although they have not contacted me. In fact, my account and mobile channel show as "Active" in the online reports and Adsense is still working on my non-mobile site and feeds.
Now I understand that things do break. I had a similar problem with AdMob once. It was quickly resolved after I sent an email to AdMob's support address. Adsense also has an address for email support, it's firstname.lastname@example.org. I sent a request for help to that address and received a reply telling me to look at the online AdSense Help Center. So I looked and of course there was nothing remotely helpful in resolving my issue. So I emailed Google again prefacing my question by saying that I'd already checked the Help Center and did not find an answer to my problem. I received the same automated reply telling me to check the Help Center. It's obvious that no human looks at requests sent to email@example.com. I also tried the online help request form at https://www.google.com/adsense/support/bin/request.py which turned out to be equally useless. All I got for my efforts was another automated response beginning with:
"Due to the high volumes of emails we receive, we're unable to individually
respond to your inquiry. Please find instant, reliable answers to all your
questions in our online help resources."
In short, there is no support for AdSense. If it works great, otherwise, too bad.
I think I know what might have caused Google to suspend my ads. On December 21st, the day AdSense stopped on my site, I ran Sphider (sphider.eu), an open source site search engine, to reindex my mobile site, something I do every week. I had just installed a new Sphider release and had to rerun the indexing program four or five times to get everything configured and working correctly. The timing suggests that running Sphider somehow caused Googe to suspend my mobile ads.
Sphider has to load every page of the site to index it, which would of course reload the ads. Sphider's page requests would be coming from my wapreview.com domain which I imagine could have triggered Google's automated fraud detection code. Still, Sphider uses an easily identifiable user agent , ''Sphider" and you would think that Google's ad bots would be smart enough to ignore indexing programs and not serve ads to them, let alone flag the traffic as abuse.
I'm pretty disappointed with Google. Not for suspending the ads but for their total and utter failure to communicate. I look at a lot of mobile sites and most are using AdMob, not AdSense. No wonder, not only does AdMob pay better but they actually respond to support requests.
If anyone has any ideas on how to get someone at Google to look at my AdSense for mobile problem, please leave a comment or use the Contact form.