Twitter opens up DMs for everyone, eliminating the need for mutual following.
Previously, if you wanted to send a Direct Message to the ice cream shop down the street about how much you love their salted caramel flavor, you’d have to ask them to follow you first. With today’s changes, the ice cream shop can opt to receive Direct Messages from anyone; so you can privately send your appreciation for the salted caramel without any barriers.
Don’t worry, it’s opt-in. If you don’t enable this, you won’t get spammed by anyone that you’re not already following.