Unintended consequences of an incentive compensation scheme?

http://money.cnn.com/2016/09/08/investing/wells-fargo-created-phony-accounts-bank-fees/index.html

"The phony accounts earned the bank unwarranted fees and allowed Wells Fargo employees to boost their sales figures and make more money."

How could WF reduce the chances of similar mistakes AND maintain a program that encourages employees to cross-sell?

Addendum:

Wells Fargo to Pay $185 Million Fine Over Account Openings
by: Emily Glazer
Sep 09, 2016
Click here to view the full article on WSJ.com

TOPICS: Principal-Agent Problem

SUMMARY: Wells Fargo, the largest U.S. bank by market value, must pay $185 million related to a regulatory enforcement action over "widespread illegal practice" around account openings, sales targets and compensation incentives. The bank fired about 5,300 employees during the government's examination. Related article: The San Francisco bank, with its folksy stagecoach logo, has positioned itself as a solid, Main Street lender that avoided the excesses of the financial crisis. That image is now in danger.

CLASSROOM APPLICATION: Students can examine the effect of sales incentives on the decisions by Wells Fargo employees to pursue underhanded sales practices. "The sales tactics and practices, which were fueled by an incentive structure that rewarded employees on the more products they sold, got out of hand, according to regulators."

QUESTIONS: 
1. (Introductory) Why do sales incentives create the willingness of employees to engage in underhanded sales practices?

2. (Advanced) What is the "principal-agent problem"? Is the Wells Fargo case an example of workers (agents) not acting in the best interest of a principal (Wells Fargo)?

3. (Advanced) What actions could Wells Fargo take to regain its positive reputation?

Reviewed By: James Dearden, Lehigh University