On the narrow issue of accounting for leaky buckets.  In fact, at least under US GAAP
accounting (the official audited accounts submitted to the Securities & Exchange
Commission), such returns are a liability.  (Actually, they are netted out of assets on
the balance sheet and out of revenues on the statements of earnings and cash flows.)  If
you look carefully at the footnotes for a firm's 10-k filing, you will say a boilerplate
paragraph on how it has estimated the appropriate provision for future returns & refunds.
So if Acme Bucket Corp estimates, based on past experience for example, that 1% of it's
buckets are leaky, it has to write down 1% of it's inventory and 1% of its bucket revenue.
  
Spencer Banzhaf