You should memorize if the memorization cost divided by the number of uses over the lifetime of the memorization is less than the information retrieval cost for

You should memorize if the memorization cost divided by the number of uses over the lifetime of the memorization is less than the information retrieval cost for a single use (e.g. multiplication tables). You should also memorize if the retrieval latency is too high for your needs (e.g. guitar chords). But I think Einstein would be a fan of web searches for a lot of memorizable information, as am I.