This thing has been going down for ages but really collapsed today (-35%) on earnings. I looked at the top ten shareholders (as of 12/31/14):
Invus Public Equities Advisors, LLC 51.94%
Fidelity Management & Research Company 10.55%
Capital Research Global Investors 6.23%
First Manhattan Company 4.88%
Millennium Management LLC 3.34%
North Tide Capital, LLC 3%
The Vanguard Group, Inc. 2.97%
BlackRock Institutional Trust Company, N.A. 2.49%
Camber Capital Management LLC 2.02%
Putnam Investment Management, L.L.C. 1.9%
There was a lot of opportunity to short this at around $15 after hours (it looks like) ... surprised it tanked under $12 during the regular session. Usually 90% of the move happens after hours, and just scraps are left for the normal market hours.