Why did Harry Drink

[jmoses22002]

No: HPFGUIDX 136069

Jmoses:
  I was just wondering if I was the only one who questions why Harry
drank the FF potion.  He has been tricked by people in disquise
before, and I thought he would be a little more careful.  Beside the
fact that Slughorn had a whole cauldron of Polyjuice Potion, he was a
Slithrin and they aren't exactly straight arrows.  Another thought I
had was, How did Malfoy get the polyjuice potion.  I would think that
a potion as potentially dangerous as that would be under closer watch.
 Please someone respond.