Who will be the customer?
The factor that is often overlooked, but critical to success relates to use cases and business models.
Assuming Silent Circle is a robust technical solution, fixed costs of entry should be relatively high, while variable costs associated with each new subscriber should be quite modest. This means they need to either narrowly target security conscious vertical market segments willing to pay a price commensurate with the value received from a mission critical application, or attempt to garner mass market adoption that allows a large number of relatively low revenue customers to offset fixed costs, with additional subscriber revenue then largely falling to the bottom line. It seems like they may be trying to walk a tightrope between the two.
I'lll be particularly interested to see what kind of "retail consumer" demand might exist for Silent Circle. My experience is that there is a dichotomy between the level of communications security protection that industry professionals imagine users need, and the level of protection most users perceive as being sufficiently valuable to pay an additional fee.