Although they are rare, they are serious enough that each requires an investigation.

BBC: Devon hospitals report serious surgical errors

Clearly there are serious problems, but they hardly look big enough to set off a crisis at the heart of the global financial system.

ECONOMIST: The crisis in the debt markets

Most businesses are reluctant to invest in cyber defenses because they don't consider an attack a serious enough threat.

WSJ: Israel's Businesses Losing the Cyber War