Google's dominance in the search market is well-documented. Its always surprised me quite a bit that Y! just cannot make any gains in its market share. Sure, Y! has more cluttered interface, its focus might be somewhere else and its algorithm might be inferior. These things are obviously fixable and it might over time.
But what makes Y! so unpardonably pathetic is that their SEM program sucks. True their overhyped Panama platform might help make some algorithmic gains over time, but why does the interface suck? They may not be smart enough to match keywords and serve ads, but c'mon guys - don't tell me you cannot a simple usable interface for your advertisers.
Between Y! and Google, the former has generally demonstrated better ability to produce fantastic UIs, but SEM is another beast. Make no mistake, Google's adwords is far from being ideal and could very well do with a more thought-through design, but Y!'s looks like a school-boy project.
If as an advertiser, where Y! clicks come at a 70% discount to Google's, if I still cannot make myself to increase my spend on Y! SEM, there is a serious problem. Not being able to drive customers to pay you is one thing; but when you do not have the etiquette to accept more money from a paying and willing customer, you are doomed, i think!