I have no conceptual issue with Amazon serving ads against search terms. My big issue with Amazon search is that they intentionally made it much less useful by removing any ability to group words into one term with quotes or exclude any term with minus. These were working features of Amazon search that had long been there (and are probably still there in the code).

With the sheer number of products and the proliferation of feature or compatibility requirements buyers have to match, removing this functionality basically breaks Amazon search. Just try finding finding an LED bulb of a certain wattage that's dimmable. Every seller of non-dimmable bulbs puts the words "Not Dimmable" in their description to reduce returns. Amazon search will return all of those, with the listings I want buried somewhere in that flood - all because they've arbitrarily chosen to disable the standard, well-understood way of solving this common problem. The only solution is using an external search engine and limiting it to Amazon.com.