Bringing the most relevant results to the user is the quest of every search engine. Fighting spam is one aspect of this issue. The other one is personalization – showing the results that would be the most interesting to the SPECIFIC searcher. Hence the localization, hence the search history….
Bing has recently followed Google on that path, applying city-based localization to the query results in the US. It will now give additional weight to local businesses, especially service providers. This is another step forward, as the local Bing searches in various countries are showing different results for quite a while already. However, for big countries, such as the States this might be not enough – so additional refinement is now applied, based on the city you are in. It must be noted, the results are not entirely different – it is just that local businesses are given some “extra points” by the search algorithm.
Another aspect is using your past search queries in the results. The Bing (as does Google for some time already) tries to “learn your preferences” based on the searches you conduct and the results you pick from the presented list. Those will be stored in search history and shown more frequently (or higher) in the result list when similar query is submitted.
It seems that “those who bought this also liked that” feature, used by many online stores and other websites is now entering the SE world.