I just discovered something interesting on my forum The Free Ad Forum. I had set my Adsense ads to show the default text/image ads. The only problem is that the same banner ads showed up over and over. Sometimes the same banner on 3 different parts of the form at one. This could not be good! Would you cover your site with the same banner all over the place? Well I changed the ads to having only one block showing text/images and the rest showing text. Earnings went up immediately. Of course. People are seeing different ads not just the same 3 banners over and over.
I heard that Google does not sell all of it's image ad space so they show public service ads (I was seeing ads for Google products too.) I guess the just did not have the variety of banners ads to keep it mixed up. This tells me it might be good to advertise with Google using banner ads. The text ads have much more variety though some of the banner ads really look great.
What do you guys think? I wrote about this on my blog too I would really appreciate any comments. Using Text Only Vs Text and Image With Adsense Ads