The idea of providing categorized results (something Hakia says they invented) is great for users as they get a nibble of each category. The user can then decide if they would rather see a full page of results for one of the presented categories. But what happens if a user selects one of the search results provided in a category directly?
To answer my question, if a user clicks a search result in a category presented on the first page, any potential ads are not displayed with that search result. The only ads that are displayed match the initial search query. The user isn't presented with any ads that match the categories on the results page. I think this hurts the experience for the user, the opportunity for the advertiser and the financial opportunity for Microsoft.
As an advertiser, I now need to spend even more time researching what categories my terms might appear in and then bid for those terms as well to even have a chance of being seen by searchers. My guess is that this will also push prices up for the main terms.
Microsoft says they are looking into displaying ads with each category in the future. As an advertiser, I hope they prioritize this change high on the list of Bing updates.