frankleeceo - 10:18 pm on Sep 9, 2013 (gmt 0)
I think the only time that you will get in trouble if the third party image ads violates the adsense guide lines. for example #*$! ads will not fly and can get your site disabled, even if those ads are not a part of your "content".
make sure that you sign with an advertiser or middle guy who safeguards the type of advertisers that they accept and display on your site. you are responsible for that much.
other than that, all image ads look quite the same with that little triangle anyways.
what you want to do is actually "not" to state which is google ads, as it can be seen as "drawing" attention to your ads. let ads be ads...displaying naturally.
i personally have used 300x250 from 2~3 different networks on the same site.