2 to 1 on your money

[minwoo]

Hi,
Often on TV, you see a player go all-in preflop and another player calls with a marginal holding such as K8, TJ, 22, etc because they are getting "2 to 1" on their money. Does this mean that you should call an all-in preflop (as long as it doesn't risk your whole stack and there is no chance of someone re-raising behind you) whenever you get 2-to-1 odds?

IE:
at 100/200, I am on button with a stack of 3000 and there are two limps in front of me, I limp on button w/ 72o(I would never do this but lets say I did) total pot size is 900 now. SB folds and BB has 900 left after posting BB. BB pushes the rest in. Folded to me so I am faced with a decision of calling 900 to win a pot of 1800. I am getting 2-to-1 odds, thus I am supposed to call. Is this correct?