@joepie91 They're also keeping history around forever. I can scroll back 8-9 years in a channel with some friends. And as we've seen from data requests they store significantly more than the contents itself whenever someone sends a message, but they're also just storing images forever.
I'm hard pressed to think that it is profitable. But I guess given the 1 billion they've got in funding maybe it can run for a while in the somewhat unprofitable range.
@rune (Mainly thinking of the file/video sharing overhead here, that gets costly pretty quickly, as well as their analytics infrastructure. The rest is probably peanuts.)