Twitter rolled out the ability for anyone to DM (direct message) you last month, and it appears the setting no longer exists on some accounts.
Found under “Settings” and then “Account,” the feature looked like this:
Since the beginning, Twitter only allowed people that you were following back to DM you.
This new feature changed that, and especially helped companies who rely off the social network for delivering customer service.
Mathew Ingram, a senior writer at GigaOm, asked Twitter about the removal of the setting, and was simply pointed towards a blog post about experiments.
I asked Twitter why the “accept DMs from anyone” feature is gone, and all I got was a link to this post: https://t.co/HMfDnHiEn6
— Mathew Ingram (@mathewi) November 18, 2013
From the blog post:
We also experiment with features that may never be released to everyone who uses Twitter. Those experiments are perhaps even more valuable because they help us decide what not to do –– which is important as we work to keep Twitter simple while improving the user experience. Ultimately, our goal is to learn and keep making the product better; we aren’t necessarily looking to launch all of the experiments we roll out.
So it could just be that the DM feature didn’t pan out, or it could further point towards Twitter’s rumored private messaging app.