<p>It’s better to work with what people already have than to require them to manage an additional network in order to use a new product.</p>
<p>You’re describing a chat service and a client for it. (Data doesn’t just go from phone to phone; it passes through a server on its way there.) It’s extremely unprofessional to couple a server to a client. A well-designed server has a published, stable API so that anyone can write a client for it and people using different clients can communicate with each other via the same protocol.</p>
<p>The most prevalent protocol, SMTP, already makes it easy to have multiple accounts on multiple servers. I myself have several email accounts that all forward to a single Gmail account, and my Gmail account is set up to be able to send emails through any of those accounts (hiding the fact that I even have a Gmail account). I also have some sophisticated filters and I could easily create a filter to send an unwanted contact’s emails straight to trash if I wanted. e.g. I have <a href="mailto:aidmbsa@live.com">aidmbsa@live.com</a><a href=“%5Bb%5Da%5B/b%5Dccount%20%5Bb%5DI%5B/b%5D%20%5Bb%5Dd%5B/b%5Don’t%20%5Bb%5Dm%5B/b%5Dind%20%5Bb%5Db%5B/b%5Deing%20%5Bb%5Ds%5B/b%5Dpammed%20%5Bb%5Da%5B/b%5Dt”>/email</a>, which I use to register for fishy websites, which forwards to Gmail. In Gmail, I have a filter that makes emails matching “to:<a href="mailto:aidmbsa@live.com”>aidmbsa@live.com</a>" skip my inbox and go to a “possible spam” folder.</p>
<p>There are already mobile Gmail clients (and generic mobile email clients) that allow account-management of this caliber. Also, emails are so fast these days that they’ve eliminated the need for real-time chat applications.</p>
<p>So if I wanted to give new acquaintances a way to contact me separately from my “main” lines of contact, I’d just give them an email address.</p>