Doing it because you can aside, I feel like if you're a handicapped person with full control of your face voice dictation would probably be a better solution.
I knew someone who had to switch to voice dictation due to RSI problems during an especially intensive work period, who ended up temporarily losing their voice through overuse. Of course that could happen with anything, overuse of a tool like this could lead to facial tics or neuralgia-like symptoms. But it's definitely got potential as an accessibility tool.
Only a matter of time before someone uses this to auto-post memes/gifs of common emotional responses.