What's with the triangle thing on tumblr?
I keep seeing it in pictures and have no idea what it means.
Ex.
http://2.media.tumblr.com/tumblr_kurh3am5Bc1qze0zio1_500.jpg
http://22.media.tumblr.com/tumblr_kus13yCIqi1qzcnnso1_500.jpg
http://13.media.tumblr.com/tumblr_kurn92Eos41qzfya1o1_500.jpg