I used to think that privacy concerns in America was strong enough to thwart ideas like single-signin and Gmail from being realized.  My study of the social networking phenomenon have gradually changed my opinion to a point where I now think the power of privacy concerns can be dispelled with the right strategy.  Obviously, this can't be done by just anyone and serious commitments must be made in terms of time and resources, but I now believe it can be done.

I have come to realize that concerns are temporal in nature and requires constant reinforcements to maintain them.  A primary source of that reinforcement is social pressures.  If people around you are concerned, you become concerned.  If they seem unconcerned, level of your concern diminishes.  People who do not conform to the group's level of concerns are pushed to the fringe and eventually casted out, either by the group or by their own choice.