I think that the point when apple accepts bitcoin for everything (app store, itunes, products), and once companies like paypal create their own solution for it (like being able to convert btc to usd in the paypal account just like any other currency), thats when it will be mainstream and used by the world.
When apple starts to accept bitcoin for things like it's app store and itunes it will likely serve as some kind of wallet service as they would want to guarantee that they get paid and so they can avoid issues with a TX never confirming. This would greatly reduce the stress on their customer service team if they have a lower number of TXs going to them.
I think all of the companies like apple, amazon, and ebay/paypal would have to develop their own payment receiving solution. If there would be one that everyone uses, it would be probably created by paypal.
I tell u guys again... dont daydream about Apple. They are not gonna accept it against their products anytime soon. First they'll try their own currency, fail and then only give it a shot. Else they'll wait for OPEC to accept it.
