1. A method for selecting ones of a plurality of content items to be cached, comprising: determining, for each of the content items, a probability of use of the content item comprising a probability that the content item will be used if cached; determining, for each of the content items, a value of caching the content item; computing, for each of the content items, a caching value estimate associated with the content item using the probability of use of the content item and the value of caching the content item; and selecting ones of the content items to be cached at least using the respective caching value estimates of the content items.