It's a bad Monday for billionaire investor Bill Ackman (HLF, ADP)

The week is off to a bad start for Bill Ackman.
Herbalife shares were up about 8% Monday morning following news that it had talks to go private.
The surge is a blow to Bill Ackman's Pershing Square Capital, the activist fund that famously went short on the supplements company five years ago while accusing it of operating as a pyramid scheme. Pershing Square's bet has largely gone the wrong way since it was put on.
Meanwhile, the human resources company ADP rejected Ackman's board nomin