A graphic example to make it more clear:
Well, how many sites did you happen to see that were showing ads with the same technique of the image above? A lot, personally I saw many web spaces that camouflage the ads in the best way their imagination suggested. And are still there after long time, not banned and not disallowed. Like this page www.seoserp.com, see? So, why Liew goes through all this? Google makes random inspections?
Maybe just the big sites (according to traffic) are the major targets of these checks, but this is the fact, don’t make google ads look to alike your web pages formatting or you may get into this bitter finding.