Throwing in my 2 cents: It looks like what Ribbon submitted to the Twitter validator was a video using the "player" card: http://cl.ly/image/2R2i1J302Z2g The player card is designed to handle embedding videos, which is what Ribbon initially showed, however when they launched their new feature they morphed the embedding options to display a custom in-stream purchase button / unit. In reality, they should have just use…
Chirpify has been enabling in-stream commerce and payments on Twitter for over a year now. Also in-stream on Instagram and Facebook. No TOS violations http://chirpify.com