[orangecat]

they were experimenting on and measuring emotions directly

Every change to an interface can potentially affect the emotions of users, whether or not you try to measure it.

[falcolas]

I won't disagree with your statement, but there's a very large difference between intentionally changing a user's mood by modifying their news feed vs. indirectly and unintentionally affecting a users mood via an interface change.

[908087]

Except in that experiment Facebook was intentionally trying to manipulate users' emotional states.