Comment by jeroenhd

> better than SMS - there is an implicit cost to send

Funnily enough, people being charged per SMS but being allowed to send as much messages as they need on apps like WhatsApp is exactly why SMS/MMS is barely used on a large scale outside of North America.

I rarely receive any spam on my phone. WhatsApp/Telegram/Signal do have the occasional obvious bot, but all apps make it trivial to block and get rid of any of them.