Even though it only lasted two weeks, I learned a lot in my first job in advertising.

It was a fill-in gig, writing ads at Auckland radio station More FM. In those days it was a stand-alone station, and it was everything the TV series WKRP had led me to expect.

The first lesson was how many seconds went into a 30-second ad.

The second was a bit less obvious. It was that the ads you run play just as important a part in people’s perception of your media brand as the content does. More FM was (and is) a mainstream music station – you could hear the same songs it played in lots of other places. Its ads, though, were mostly unique. Most of them only played on More FM and had a big impact on what people thought of the station.

I was thinking of that the other day when I saw the banner ad I’ve placed at the top of this post.

It does Trade Me no favours at all, and for every dollar the advertiser is paying for it to be there, it’s taking $10 off the value of the Trade Me brand (figures approximate, but you get my point).

Advertising like that might bring in a few bucks, but it cheapens Trade Me and, critically, harms the trustworthiness it’s spent over a decade building. Does that ad look like it comes from a trusted company? Does it seem 100% legitimate? Would you click on it?

(It may well be all those things, but we’re talking perception here, which is WAY more important than reality.)

Trade Me doesn’t care. I asked them. They’re OK with it (although they agree that the ad is “unglamorous”).

Z Energy (who are not associated with the ad at all) says there’s nothing they can do about the advertiser using their brand in that way. (I doubt that though.)

There’s been a bit of media chat about this happening in the opposite sense: Google AdSense placing brands’ display ads on sites and blogs that, had they known, they’d rather not be on.

But it works both ways. Site visitors don’t care that some of your website is yours and some is delivered by advertisers. Together they form a picture. And if a big, ugly, lurid part of that picture doesn’t feel worth trusting then you’ve thrown away the most valuable thing you own.