23. A computer storage medium encoded with a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: obtaining first profile data for a first user that is associated with a computing device; obtaining second profile data for second users that submitted search queries, the second users being different from the first user; determining, based on the first profile data and the second profile data, similarity scores that are each indicative of a degree of similarity between the first user and at least one of the second users; selecting a proper subset of the search queries based on the similarity scores; generating an update for an autocomplete cache of the computing device associated with the first user using the selected subset of the search queries; and providing the update to the computing device associated with the first user.
23. A computer storage medium encoded with a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: obtaining first profile data for a first user that is associated with a computing device; obtaining second profile data for second users that submitted search queries, the second users being different from the first user; determining, based on the first profile data and the second profile data, similarity scores that are each indicative of a degree of similarity between the first user and at least one of the second users; selecting a proper subset of the search queries based on the similarity scores; generating an update for an autocomplete cache of the computing device associated with the first user using the selected subset of the search queries; and providing the update to the computing device associated with the first user. 33. The computer storage medium of claim 23 , wherein: obtaining the first profile data for the first user comprises obtaining a first search query history for the first user; obtaining the second profile data for the second users comprises obtaining second search query histories for the second users; and determining the similarity scores comprises determining the similarity scores based on commonalities between the first search query history and the respective second search query histories.