Re: Pardon my ignorance...
@fidodogbreath "Pardon my ignorance... ...but do iPhone users have to use iMessage for SMS?"
Simple answer is No. You can turn off iMessage which defaults everything to SMS/MMS which your mobile network charges for accordingly. Only downside is they haven't implemented SMS delivery reports - read reports are only available if you use iMessage.
If you turn on iMessage the iPhone will attempt to use iMessage for everything it can, only dropping back to SMS/MMS where the recipient doesn't have an iPhone*, has an iPhone with iMessage turned off* or there's no data connection.
In my case I leave iMessage off - SMS for text, then use email if I want to send pics. If GCHQ really think my ramblings are worth intercepting they can go to a court in the UK to get permission wiretap my carrier rather than asking the NSA to do it for them via Apple's servers.
*I think the iPhone queries Apple's servers to check if the recipient has an iPhone and is/isn't using iMessage. I suspect this is how the phone determines if a contact can receive a Facetime connection also.