John Gruber, reacting to this post from Lauren Goode about iMessage stickiness:

There’s a split between iPhone users who are primarily part of the Apple ecosystem (iCloud, Safari, Apple Mail, …) and those who are part of the Google ecosystem (Google Drive, Google Calendar, Chrome, Gmail, …).

iMessage is an exception. With iMessage you get to connect both with iPhone users in the Google ecosystem and iPhone users in the Apple ecosystem. For a lot of us here in the U.S., that’s just about everyone we know. It’s no coincidence that two of Google’s major Android initiatives this year are Allo and Duo, their answers to iMessage and FaceTime. I don’t think it’s going to work.

And:

As an iOS/MacOS exclusive, iMessage is a glue that “keeps people stuck to their iPhones and Macs”, not the glue. iMessage for Android would surely lead some number of iPhone users to switch to Android, but I think that number is small enough to be a rounding error for Apple. Apple wins by creating devices and experiences that people want to use, not that they have to use.

Both Lauren Goode’s original and Gruber’s reaction posts are interesting and worth reading.