1. A method of providing rewards based on interactions with annotations, the method being implemented by a computer system that includes one or more physical processors executing one or more computer program instructions which, when executed, perform the method, the method comprising: receiving, at the computer system, a first annotation provided by a first user during a presentation of a first content item, wherein the first annotation corresponds to a reference time at which a product or service appears in the first content item, and wherein the first annotation is provided by the first user via a user device different from the computer system; identifying, by the computer system, in the first annotation, a reference referring to the product or service; modifying, by the computer system, the first annotation to include a mechanism that enables a transaction related to the product or service, wherein the first annotation is modified to include the mechanism based on the identification of the reference; associating, by the computer system, the modified first annotation with a first user account of the first user; providing, by the computer system, based on the corresponding reference time, a presentation of the modified first annotation during one or more presentations of the first content item to other users such that the mechanism is available for use by the other users via the modified first annotation during the one or more presentations of the first content item; monitoring, by the computer system, during the one or more presentations of the first content item, use of the mechanism by the other users via the modified first annotation; and determining, by the computer system, a reward to be provided to the first user account based on the monitored use of the mechanism by the other users via the modified first annotation.
6. The method of claim 1 , wherein monitoring the use of the mechanism comprises identifying an execution of the transaction enabled via the mechanism in the modified first annotation, and wherein the reward is determined based on the execution of the transaction.