There are certain market segments that privacy and security are a "must have." That may be a relatively small slice when you compare it to something like Facebo

There are certain market segments that privacy and security are a "must have." That may be a relatively small slice when you compare it to something like Facebook, but since Zimmerman is not trying to scale a free service that "small slice" may be significant revenue. Having said that I do agree that this service won't sell to a wide audience.