Saying Google and Facebook have built successful businesses around free services is like saying dairy farmers have built successful businesses around offering cows free grass.
If you use BitPay as a payment processor I don't think it would be as easy as, say, swapping out BTC addresses, because of different implementations of webhooks and other APIs.
I won't use Bitcoin if transfers aren't free. Bitcoin is competing with my bank account, and to date I can transfer money all around the EU for free, and I've been doing so since 2006. I my case, Bitcoin won't work if the level of service is any worst/more expensive than my bank.
"With USA.NET® Net@ddress®, ... have one email address for the rest of your life for free!"
http://web.archive.org/web/20001218082700/http://usa.net/per...
I'm not buying into free + forever.