Farm impressions and pageviews as you go for conversions with pretty ads! Naturally, if the user's eye does not target the ad, even indirectly, a well-designed ad will certainly improve the overall look & quality of the publication itself, thus helping its cred along. The concept of less is more does not always apply; it depends on what you're designing for and for whom. Fun stuff, lots of space for variation here.

If Nike's logo suddenly became an ornate portrait of a rooster encased in a block of ice, would they sell fewer sneakers? What if we gave the rooster a hat? How about if Apple, today, thought differently and went with only lime green backdrops & orange speckles, how long would it be until their stock prices wavered? Even using an incredibly established brand, invariably the obvious conclusion is that giving your tech startup a visual style to match the Vatican's would confuse the hell out of prospective users. A decent deal of a graphic style's success in identity depends upon the marketing context of its time & competitors; due to this, it's advisable to error on the side of iconic.