i don't think blending is forbidden .... but i think what is forbidden is what is done on mfa sites where everything is a link and you can't tell adsense links from other links
i think if blending was forbidden they would take a way the option to customize ads...
jmo
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- Think for yourself - Think outside the box -
from the sounds of it blending is forbidden... customization can also be used to make ads stand out or compliment existing colours on your site, and isn't used only to match and blend links with content.
There's blending (making the ads "fit" pleasantly with your site) and there's deceptive blending (tricking visitors into thinking the ads are site content or internal links). I get the impression the second is what they're trying to eliminate.
For a long time, if you chose to have headers for your ad blocks they either had to say "Advertisements" or "Sponsored Links". No other header text was allowed. I've seen some pretty misleading titles since they lifted that restriction - could be that they're regretting it.
you got some shocking news there 
