The Mind Blowing Math 'Proof'

I always felt Math is a fun thing to play with, until recently someone showed me the following:

Prove: 1 + 2+4+8 + ....  = -1

Proof:

1 + 2+ 4 + 8 + ... = (2-1) (1 + 2+ 4 + 8 + ...)

                               = 2*(1 + 2 + 4 + 8 + ...) - ( 1 + 2 +4 + 8 + ....)

                               = 2 + 4 + 8 + 16 + ..... - 1 -2 -4 - 8 - 16 - .....         [You can see, first 2 and later -2 canceled, etc]

                               = -1

So we just proved 1 + 2 + 4 + 8 + ... = -1.     

Infinity is not a good thing. :-)