Is there a difference between parashat zachor and all other Torah readings during the year? If there is, would each individual be required to read parashat zachor to himself instead of relying on the reading of the ba'al koreh? Rav Yosef notes that there are at least two differences between the weekly keriat Ha-Torah and the reading of parashat zachor. First, zachor is d'oraita while the weekly readings are d'rabbanan. Second, the weekly readings are a mitzva incumbent on the community, while the reading of zachor is an obligation on each individual. Given these two differences, there is certainly room to say that one should have to read zachor by himself, even if only from a Chumash.
However, Rav Yosef concludes that one can rely on the ba'al koreh via the principle of shomei'a k'oneh. As proof, he notes that while each individual has an obligation to recite kiddush, standard practice is for one person to make kiddush on behalf of many other people, and for them to fulfill their obligation via shomei'a k'oneh.