yohaas - 2:49 pm on Feb 14, 2012 (gmt 0)
I think that paragraph in the Adsense TOS is referring to communication about ads displayed using Adsense. For example, if Adsense displays an ad that I feel is inappropriate, I would need to contact google about it and not go directly to the advertiser. It's not saying that you need to ask google permission before displaying other ads.
Also, the Adsesne help says this:
"You're welcome to display Google ads on the same site or page as other third party advertisements provided that the formatting or colors of the third party ads is different enough from that of the Google ads."