Widespread scorn hasn't seriously impeded Facebook's Messenger app, which is now used by more than 500 million people.
The app enables users to send texts and photos to their Facebook friends in a way similar to SMS messaging.
It first launched in 2011, but was given a jolt in August when Facebook stopped allowing messaging on the general app.
The decision forced users to either download the Messenger app or forfeit their ability to message their Facebook friends.
Many reacted angrily, writing withering reviews on app stores.
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Yet Messenger is now used by more than half a billion people at least monthly, said Facebook's chief product manager Peter Martinazzi in a blog post.
That makes it one of the most popular messaging apps in the world.
Messaging giant WhatsApp, which is owned by Facebook, had about 600 million users in August.
