The thing is, everyone I know uses Facebook the website but hates Facebook the company. I don't see the Facebook brand selling phones (I recall they rated on the bottom of brands in some study).
People hate everything. The big banks and airlines all rate at the bottom of customer satisfaction surveys, and yet they're big because everyone does a lot of business with them. People complain, but they don't change who they do business with. I think a Facebook phone will be massively successful on name alone.
As a simple example more people are starting to use credit unions: http://www.recordonline.com/apps/pbcs.dll/article?AID=/20100...
Change is never instant, it takes time for alternatives to develop and for people to buy in.