This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
If an offer has been made to the general public, as by advertisement, such offer may be revoked by a similar advertisement, even if such revocation does not come to the knowledge of one who accepts such offer after such revocation has been published;1 or by other equally public means;2 as well as by actually communicating notice of such revocation to some specific person in order to revoke such offer as to him. In offers of this sort, it is impracticable to give actual notice to every person who may have read the original offer, since the offeror has no means of knowing to whom to give such notice of revocation. Accordingly, the courts must either hold that such revocation is sufficient if it is given the same publicity as the original offer, or else they must hold that for practical purposes such an offer is irrevocable, although it is not for value and is not under seal, while this rule is said to be "a rather strong piece of judicial legislation."3