11. A system comprising: one or more processors; a memory storing instructions that, when executed by the one or more processors, cause the system to: host a social network comprising a plurality of communities associated with a plurality of users; identify, from the plurality of communities, a set of communities that a first user belongs to; determine a list of classifications for the first user based upon the set of communities; determine a degree of personalization based on an amount that the first user has participated in each community of the set of communities; determine personalization information from the list of classifications associated with the first user and the degree of personalization; generate a personalized search query based upon the personalization information; and search a content index using the personalized search query to produce a search result set comprising documents relevant to the personalized search query.
11. A system comprising: one or more processors; a memory storing instructions that, when executed by the one or more processors, cause the system to: host a social network comprising a plurality of communities associated with a plurality of users; identify, from the plurality of communities, a set of communities that a first user belongs to; determine a list of classifications for the first user based upon the set of communities; determine a degree of personalization based on an amount that the first user has participated in each community of the set of communities; determine personalization information from the list of classifications associated with the first user and the degree of personalization; generate a personalized search query based upon the personalization information; and search a content index using the personalized search query to produce a search result set comprising documents relevant to the personalized search query. 17. The system of claim 11 , wherein the instructions, when executed, further cause the system to automatically determine the personalization information from online activities and consumer information of the first user on the social network.