2. The method of claim 1 , wherein the plurality of items of content comprises a first item of content associated with first metadata in the associated metadata; wherein the first item of content indicates a first reason for the person to perform an action, the reason comprising information about a subject of the action; and wherein the first metadata comprises: a first value, determined based at least in part on information about the person, indicative of how persuasive the first reason is likely to be to the person; and a second value, independent of any information about the person, indicative of how persuasive the first reason is likely to be to any person.
2. The method of claim 1 , wherein the plurality of items of content comprises a first item of content associated with first metadata in the associated metadata; wherein the first item of content indicates a first reason for the person to perform an action, the reason comprising information about a subject of the action; and wherein the first metadata comprises: a first value, determined based at least in part on information about the person, indicative of how persuasive the first reason is likely to be to the person; and a second value, independent of any information about the person, indicative of how persuasive the first reason is likely to be to any person. 3. The method of claim 2 , wherein the reason for the person to perform an action comprises a reason for the person to purchase a product.