If you've noticed that Instagram photos in your Twitter steam look a little less-than-optimal (horrible and cropped), it's not just you. Twitter users everywhere are experiencing the problem ans Twitter is well aware of it.
But Twitter says they are not to blame. Twitter blames Instagram, saying that it's disabled its Twitter cards integration and that's the cause of the problem:
Users are experiencing issues with viewing Instagram photos on Twitter. Issues include cropped images. This is due to Instagram disabling its Twitter cards integration, and as a result, photos are being displayed using a pre-cards experience. So, when users click on Tweets with an Instagram link, photos appear cropped.
Twitter cards is a design feature that allows for content creators to ensure Twitter users have a media-rich experience with their content. You've surely seen Twitter cards in action - for instance when an article from the New York Times appears in your stream and it appears expanded with a photo and part of the article text. That's a Twitter card.
But now that Instagram's dropped its support of Twitter cards, photos are appearing cropped and well, crappy. This seems like just another side effect of Facebook's Instagram acquisition. Rawr.
It's possible that in the future, Twitter won't even need Instagram photos to make their service media-rich. Well, that's the plan at least. Recent reports suggest that Twitter may be developing native photo filtering. Just how much that would cut into the Instagram market share on lo-fi photo shares is unknown, however.