Why has Instagram blocked Twitter?

Instagram accumulated a million users within two months of going on Apple's AppStore (AFP/Getty Images)

This week Kevin Systrom, chief executive of Instagram, the photo-blogging service owned by Facebook, spoke at the LeWeb conference in Paris, where he explained why Instagram has blocked Twitter from displaying photos taken as "cards" on its service. Confused? The Guardian's Charles Arthur isn't. Here's the gist of his piece, about how the social network war is reaching new levels.

"The effect of Instagram cutting off integration with Twitter's 'cards' system means that the content doesn't necessarily display accurately, with cropping being used on some photo shapes. Systrom said in a statement that Instagram previously supported Twitter cards 'because we had a minimal web presence' - the app only existed on mobile phones, and it was difficult to find photos via the web. But now, Instagram is developing a more web-based interface - with support for Facebook 'likes' - and feels that 'the best experience [for users] is for us to link back to where the content lives.' Meanwhile, Twitter is reported to be working on Instagram-like photo filters - a move that would let it catch up to Instagram, though it would add a layer of complexity to a service whose principal attraction has frequently been its simplicity - as well as the content."