Twitter has made their nut as the collective tissue of the social web. Sure the tweets are actual content, but they're always about something external -- twitter is most often used for seeing what people have to say and share about something else. If they move into photos that's a move into primary content, it means they're no longer just dealing with hosting the connective tissue - photos, videos, blogs are the meat. I dont have any conclusion to draw from there, because im conflicted. Philosophically that really bugs me, but practically I'll probably use it.