Eventually, p = 0 catches up to you

Especially if it is a product consumers wish to bring home:

In Fairfax, officials more than doubled the inventory of e-book copies from 2010 to 2011, to more than 10,000, but demand for the books tripled in that time. Now the average wait time is three weeks. Of course, there can also be lengthy waits for hardcover and paperback books, although those waits are usually for current bestsellers while older titles are generally available.

By contrast, on a typical day, about 80 to 85 percent of the system's e-books are checked out, said Elizabeth Rhodes, the collection services coordinator for the Fairfax library system. But after the holidays, when many people received e-readers, 98 percent of the collection was spoken for.

Here is more.