For the record, they almost certainly overreached elsewhere but imo, what was done with this app is pretty fair and balanced.
It's much better than requiring backdoors in apps or services. It's almost like real police work.
Is this a thing? A specific type of prepaid phone or maybe a “laundered” sim card?
and it was invite only...
1. There is a well known adage that goes something like, 'if the service is free, you're the product.' One could easily think the inverse is true ('if you're paying for the product, you're the customer') but obviously in the light of this case it isn't necessarily so. But making users pay for the service likely decreased their level of suspicion.
2. Need to tie a pseudonym to real person? A credit card number, bank account, or even a bitcoin public key get you a long way toward that goal.
I need to go find a copy of the adverts and spec for this product.. i'd love to know how they got around lying to their customers.