Arguing that you don't care about the right to privacy because you have nothing to hide is no different than saying you don't care about free speech because you have nothing to say.Edward Snowden
You don't even need to give an email address.
We think it's important for everybody to be able to interact with the world anonymously. SMS Privacy allows users to acquire phone numbers, for sending and receiving SMS, without any links to their real-world identities.
To help users preserve the separation between their SMS Privacy accounts and their real-world identities, we ask for only minimal information on the signup form (only a username and password is required). We made the decision not to require an email address because it is getting increasingly difficult to obtain an email address that is not linked to a real-world identity, although SIGAINT and ProtonMail do provide privacy-preserving email accounts.
Making a payment with PayPal or a credit card is another way online activity is connected back to a real-world identity. We accept payment in Bitcoin only, so that there is no intermediary who knows your personal information.
It is perfectly possible to use SMS Privacy in a way that is not completely private. For example if you send funds straight from a Bitcoin exchange to SMS Privacy, the company operating the Bitcoin exchange will know you are using SMS Privacy. We believe ultimate responsibility for preserving privacy lies with the end user. You should take whatever steps you consider appropriate to defend against your hypothetical adversary. SMS Privacy (like anything else) is not a complete solution for anonymity, it is a tool that helps you.