this is genius.  guiding and restrictive but within an encouraging ux.  if you're trying to glean *why* something is interesting to someone for your machines to have something to learn on (hunch's biz, if you weren't aware), you need people to take the time to write a few words. (from an seo perspective, a bit more than a few, but that's another kettle of organic stew.) 

when you want to recommend something in the hunch ui, a comment box appears below in a smooth, quiet (yes. quiet.) animation.  you have to write a few words.  you can't not write a few words. you can press the submit button but nothing happens other than a color state change on the button. you can't just press the recommend button and then the submit button and slip out through the back door without adding your voice.  you're literally like 'oh. okay. if i have to write something to get this button to push, then i might as well write something. 

and then you feel better. it's like a thank you note; you dread writing it, and you actually have to think of something to say (if you care at all), but then when you're done, you feel good. you wrote a thank you note.

anyway it's super cool.