1. A computer-readable storage media storing computer-readable instructions that, when executed, instruct a processor to perform operations comprising: receiving annotations from a plurality of client devices; identifying tags associated with at least a portion of the annotations; forming a group associated with a plurality of members, each of the plurality of members being associated with a client device of the plurality of client devices; receiving a request from a respective client device of a member of the group to obtain tags utilized by an additional member of the group and matching a criterion specified by the request; identifying a tag that is utilized by the additional member of the group and that matches the criterion of the request; and sending the tag to the respective client device.
1. A computer-readable storage media storing computer-readable instructions that, when executed, instruct a processor to perform operations comprising: receiving annotations from a plurality of client devices; identifying tags associated with at least a portion of the annotations; forming a group associated with a plurality of members, each of the plurality of members being associated with a client device of the plurality of client devices; receiving a request from a respective client device of a member of the group to obtain tags utilized by an additional member of the group and matching a criterion specified by the request; identifying a tag that is utilized by the additional member of the group and that matches the criterion of the request; and sending the tag to the respective client device. 3. The computer-readable storage media of claim 1 , wherein the operations further comprise: receiving one or more additional tags utilized by at least one of the members of the group; and providing updated tag information to the members of the group, the updated tag information including the one or more additional tags.