[mtgentry]

'The “pin” button remains inactive until the user types something. Anything. Might this count as “criticizing” or “commenting”?'

Interesting. I'd like to see a court case further define what constitutes a "comment" on the web. Other sites do this too, for example Buzzfeed.com's entire business model is based on taking content from bloggers and then hosting it on their own site, without providing any kind of insightful comment.

http://www.buzzfeed.com/mjs538/if-both-of-angelinas-legs-wer...

[anothermachine]

"commenting" is only one aspect of fair use, and it generally is interpreted to mean "copying a small snippet as an example" or "reproducing a low-resolution copy for reference" to provide context.

Another aspect of fair use is "not depriving the owner of their own commercial use of the work".