Twitter employees brag about reading users' private messages

[Mister Obvious]

At least "three or four hundred people" (8:08) paid to go through direct messages (DMs). 

Computer algorithms go through everything you post on Twitter (and Facebook, and everywhere, see 4:16) and "build a profile" about you based on keywords (your "interests")...

And my guess is when certain keywords are found, that's when the employees are alerted to manually read your messages.