Problem is the competition. You've got stuff like superrewards and what not that allows you to get free game points or buy them directly through them. And the big one like a freight train coming is facebook's points. They are as big as google. So why would someone buy bitcoins to buy game points when they can just have facebook take care of it for them?
And without installing the software... you are trusting in a 3rd party just like you do for paypal and the such.
I don't see it as competition for offer-based systems like superrewards. But there are lots of people who can't be bothered earning virtual currency by filling out surveys etc.
Yes, FB points is a threat. As I understand it FB takes a big slice of the pie though. That is where bitcoin has the advantage from a developer's perspective. Assuming FB doesn't ban all competitors.
Who knows how long it will take FB to do that though. In the meantime, much exposure could be gained for bitcoin.