Nortel Accounting Fraud?

Take a darling of the stock market, add a spectacular fall, throw in a possible recovery and then sprinkle the whiff of scandal in the Executive Suite.  The newest Hollywood business blockbuster?  No, the Nortel fraud case.

In a nutshell, senior executives, including the Chief Financial Officer, have been charged with manipulating the company's earnings in order to earn themselves a bonus.

I don't know the facts of the case, as all I have read are the newspaper accounts.  The reality is that accounting involves estimating of the impact on future events on current operations.  For example, if you guarantee your products, you know that you will have to refund some amounts to customers in the future.  How much?  Only experience can tell, and even then, it's often wrong.  So, you estimate.  A technical person will give you some rule, like 1.25% of the products will fail, so you calculate how many you have sold and set aside 1.25% (or more if you will incur additional service costs).

As an accountant, my goal is that the financial statements of a company reflect the economic activity of that company over time, but please don't hold me to one specific number, particularly the Net Income.  That just isn't realistic.

What I want to know is:  who created a significant bonus scheme based solely on accounting income?  What were they thinking?