Should investors worry about the possibility that business value may decline? Absolutely.

The possibility of sustained decreases in business value is a dagger at the heart of value investing (and is not a barrel of laughs for other investment approaches either). Value investors place great faith in the principle of assessing value and then buying at a discount. If value is subject to considerable erosion, then how large a discount is sufficient?

Should investors worry about the possibility that business value may decline? Absolutely. Should they do anything about it? There are three responses that might be effective.

• First, since investors cannot predict when values will rise or fall, valuation should always be performed conservatively, giving considerable weight to worst-case liquidation value as well as to other methods. 
• Second, investors fearing deflation could demand a greater than usual discount between price and underlying value in order to make new investments or to hold current positions. This means that normally selective investors would probably let even more pitches than usual go by. 
• Finally, the prospect of asset deflation places a heightened importance on the time frame of investments and on the presence of a catalyst for the realization of underlying value. In a deflationary environment, if you cannot tell whether or when you will realize underlying value, you may not want to get involved at all. If underlying value is realized in the near-term directly for the benefit of shareholders, however, the longer-term forces that could cause value to diminish become moot.

Ref:  Margin of Safety by Seth Klarman