In the case of the Challenger, the culprit was a simple O-ring that had become too brittle to do its job after a freezing night waiting on the launch pad.

FORBES: BP Oil Spill Investigation Will Focus On Blowout Preventers

The wedding ring was simple ruby, designed by Zuckerberg.

FORBES: Facebook's Zuckerberg "Likes" Chan; Marries College Sweetheart

Her favorite new piece of jewelry is a simple bracelet attached to a ring.

WSJ: Summer Evening Wear That's Both Light and Chic

The top lot at the Oct. 19 sale is a rare, internally flawless pink diamond weighing 25 carats, set in an elegantly simple rose gold and platinum ring, flanked on either side by a petite pear-shaped diamond.

FORBES: Rocks Under The Hammer

But in a concession, the Banking Commission proposal agreed to the use of simple derivatives, such as currency hedges, for banks within the ring-fenced body.

BBC: Business

Peacekeeping, however defined, may be an easier job than fighting the Islamists, but holding the ring between the various non-Taliban parties is far from simple.

ECONOMIST: At last, signs of hope

Instead, a simple band studded with black diamonds or black jade, worn on the right hand's ring finger, can add some oomph to a suit while still being appropriate, he says.

WSJ: Ways to Make a Manly Statement With Jewelry