While Yahoo! succeeded in turning lemons into lemonade, taking unsold inventory and using it to support in-house businesses to help monetize their traffic, the ads they run to do this are quite terrible. The net effect of seeing so many Yahoo! ads (they seem to have invaded every category) leads to a cheesy brand impression. They run the risk of becoming the K-Tel of online advertising, which isn't a very good creative corner in which to paint yourself.
Yahoo! is to be admired for its hutzpah in using its own ad inventory to develop profitable in-house businesses. It's an example more media vehicles should choose: faced with huge lots of inventory, coupled with irrational reluctance on the part of advertisers to buy it, the natural answer is to beat the advertisers at their own games.
This has lead to the creation one of the largest dating services, one of the biggest web hosting businesses and forays into many other businesses. The problem is, the branding associated with each of these services has clearly been happenstantial. While Yahoo! does spend money branding itself with an advertising campaign, these impressions are a drop in the bucket relative to the billions of impressions run with creative that obviously took someone about a half hour to create.
Like it or not, viewers have come to expect Yahoo! to be the kind of company to slap some text together, maybe with some clip art, maybe not, and a "click here" action statement. This is the moral equivalent of the local used car ad.
The "design" sensibilities used to make an easily navigable search engine are not the same sensibilities a company needs to apply to its brand. The advertising efforts to date suffer not so much from poor designers, but the wrong designers.
To turn things around, Yahoo! needs some outside help. It's not that they don't have extremely talented people in-house, it's just that developing a brand and putting some brand discipline into communications requires an interactive process with an unbiased partner.