Ed Bronfman, Jr. is a scion of the family that used its ownership of Seagrams, and U.S. liquor prohibition, to build a fortune in Canada.  Eventually he made a very large investment in Warner Music and appointed himself CEO.  Unfortunately, his investment has not turned out as well as he would have liked due to market shifts in how people buy music.  Here’s his quote (source of quote here):

"We expected our business would remain blissfully unaffected even as the world of interactivity, constant connection and file sharing was exploding.  And of course we were wrong.  How were we wrong?  By standing still or moving at a glacial pace we inadvertently went to war wtih consumers by denying them what they wanted and could otherwise find – and as a result, of course, consumers won."

Lock-in caused Warner Music to be complacent – and ignore customers that switched to competitors.  When markets shift, standing still (doing the same thing – or Defending & Extending your old Success Formula) can cause you to become competitively less viable.

Here’s an even better quote from Bill Gates, founder of Microsoft (source of quote here):

"Your most unhappy customers are your greatest source of learning."

Listening to your biggest, and your best, customers is important, but you won’t learn much about the market.  They like your Success Formula and share your Lock-ins.  It’s the customers who complain that are telling you about changes in the marketplace.  They are telling you they will shift if they can find an alternative.  And those who outright become disloyal, who leave, are really able to tell you about market shifts and changes in competition that threaten your returns.  You might want to take your best customer golfing to keep her happy, but you should invest your resources in understanding the customers that complain, threaten to leave, cut their business or completely leave.  They can give you the market information you need to plan for a future with higher returns.