I think merchants play a bigger role then consumers.
Why?
Well simply if consumers find a lot of merchants accepting bitcon it will create awareness and people will be intrigued.
Visiting the bitcoin.org website they will find so many advantages that they eventually will try it.
I agree with this. More merchants who accepts Bitcoin as a payment option, more people will be curious and will test use of Bitcoin. Much better if there will be a popular online store who will come up with a Bitcoin only day payments to increase awareness of Bitcoins.