15. A server device comprising: a memory to store a user profile that includes an author likelihood score of a particular user, where the author likelihood score estimates a likelihood that the particular user will become an author of comments; and a processor to execute instructions to: determine the author likelihood score for the particular user, receive one or more implicit requests for comments for a particular document from users, the one or more implicit requests for comments being associated with the users selecting a visual object to view comments associated with the particular document, receive an indication that the particular user has accessed the particular document, determine, after receiving the indication, that the particular document has been identified as needing comments when a quantity of the one or more implicit requests for comments, received for the particular document, exceeds a threshold, determine whether the author likelihood score of the particular user is greater than a particular threshold, when the particular document has been identified as needing comments, and provide a suggestion to the particular user to write a comment about the particular document when: the author likelihood score of the particular user is greater than the particular threshold, and the particular document has been identified as needing comments.
15. A server device comprising: a memory to store a user profile that includes an author likelihood score of a particular user, where the author likelihood score estimates a likelihood that the particular user will become an author of comments; and a processor to execute instructions to: determine the author likelihood score for the particular user, receive one or more implicit requests for comments for a particular document from users, the one or more implicit requests for comments being associated with the users selecting a visual object to view comments associated with the particular document, receive an indication that the particular user has accessed the particular document, determine, after receiving the indication, that the particular document has been identified as needing comments when a quantity of the one or more implicit requests for comments, received for the particular document, exceeds a threshold, determine whether the author likelihood score of the particular user is greater than a particular threshold, when the particular document has been identified as needing comments, and provide a suggestion to the particular user to write a comment about the particular document when: the author likelihood score of the particular user is greater than the particular threshold, and the particular document has been identified as needing comments. 16. The server device of claim 15 , where the processor is further to: receive one or more explicit requests for comments for the particular document from one or more users, where the one or more explicit requests for comments are associated with the one or more users selecting a visual object to request comments about the particular document when the particular document is a document without comments, and identify the particular document as needing comments when a quantity of the one or more explicit requests for comments, received for the particular document, exceeds a threshold.