One example of a company that actually did make large repurchases of shares substantially below book value in 2011 is American Capital ( NASDAQ: ACAS), which announced it bought back millions of shares of its own stock, at prices considerably below its most recent reported book value per share, thereby elevating the per-share book value of the remaining shares.

FORBES: The Importance of Book Value

If the opportunity arose for Berkshire to be able to buy back shares below its book value, some cash would be used up, thereby reducing assets, but each remaining shareholder would represent a slightly greater ownership percentage of the company and the intrinsic value of the remaining shares would climb.

FORBES: The Importance of Book Value