1. A method of hosting electronic conversations, comprising: at a computer system having one or more processors and memory storing programs for execution by the one or more processors, maintaining a plurality of conversations, each having an identified set of participants; maintaining for each respective participant in one or more of the conversations, a respective participant-specific inverse index of terms in conversations for which the respective participant is an identified participant; in response to receiving a search query from a first participant of a first conversation in the plurality of conversations: using the participant-specific inverse index corresponding to the first participant to identify a second conversation in the plurality of conversations as relevant to the search query, and formatting all or a portion of the second conversation for display to the first participant; wherein the plurality of conversations are instant messaging conversations, and participants in each conversation in the plurality of conversations are instant messaging participants.
1. A method of hosting electronic conversations, comprising: at a computer system having one or more processors and memory storing programs for execution by the one or more processors, maintaining a plurality of conversations, each having an identified set of participants; maintaining for each respective participant in one or more of the conversations, a respective participant-specific inverse index of terms in conversations for which the respective participant is an identified participant; in response to receiving a search query from a first participant of a first conversation in the plurality of conversations: using the participant-specific inverse index corresponding to the first participant to identify a second conversation in the plurality of conversations as relevant to the search query, and formatting all or a portion of the second conversation for display to the first participant; wherein the plurality of conversations are instant messaging conversations, and participants in each conversation in the plurality of conversations are instant messaging participants. 5. The method of claim 1 , wherein the set of participants of a respective conversation include one or more subscribers of the computer system and an email participant identified by an email address.