When we first wrote about Instance (then known as Itsdagram) we talked about the issues around the Instagram terms of service. It's worth recapping this here:
As we've previously explained Instagram's official API only allows read-only access to the service. It is not possible to upload photos, or register a new user, using the publicly documented Instagram APIs. That doesn't mean that such APIs do not exist, rather it means Instagram does not want third party developers using them. Instagram's own apps for iOS and Android do use these APIs and Itsdagram works by reverse engineering these undocumented APIs.
Using these non-public APIs in a third party app is a clear violation of Instagram's terms of service. Apps that do this break section 10 of Instagram's terms of service ("you must not access Instagram's private API by means other than those permitted by Instagram") and will likely also in violation of section 2 of Instagram API's terms of sevice ("you shall not use Instagram APIs for any application that replicates or attempts to replace the essential user experience of Instagram.com or the Instagram iPhone App"). Theoretically, this could lead to the suspension or deletion of an account that uses such an app, although in practise this is unlikely.
For the last three months Instagram has taken no action against third party apps accessing the service from a Windows Phone device. Today's news suggest that has now changed, although it is not clear exactly how Instagram is identifying Windows Phone users. In a tweet Daniel Gary, Instance's developer, says that images are successfully uploaded to Instagram, but are deleted shortly afterwards. Using the same account with an official client (on iOS and Android) works without any issue. This suggests Instagram has some way to detect those using the Instance app, and is deliberately taking action against them, rather than blocking at an account level.
Daniel Gary says he is looking to fix the problem, but as of last night had yet to find a solution. It is entirely possible that a work around can be found, but there's no guarantee that Instagram wouldn't take further action to block access once again. Once this sort of things starts a tit-for-tat pattern can soon emerge.
The changes that Instagram have made may also impact other Windows Phone app using the Instagram API unofficially (or at least be vulnerable to a similar block if they get popular). That will leave Windows Phone users with the choice of using an app that doesn't use the API (e.g. Instagraph), or who have been given official permission to use the API (e.g. Hipstamatic Oggl). The former may also end up being blocked, especially if Instagram is looking to block unofficial apps on Windows Phone more generally, but the latter will continue to work as it has a formal agreement in place with Instagram. The issue with Oggl is that it only allows for uploads, and would need to be combined with an app like Metrogram to get the "full" Instagram experience.
Update @ 16:09 GMT
The Verge report that the block is due to a change in the Instagram API, specifically the way in which the system fights spam attacks. The blocking of Instance may be an unintended consequence, rather than a deliberate act. Further it will apply to all third party apps using the unofficial Instagram API.
Instagram has said many times that it wishes to have full control over images uploaded to its service, which is why the upload API is not public, but how active the company has been in blocking third party apps is open to debate.
Here's the official statement from Instagram:
"We recently made an update to the systems that we use to fight spam to help prevent future attacks and increase security. As part of this, applications accessing Instagram against the terms of our API may also be affected. This update does not specifically target any particular app or platform."
Update 2 @ 21:31
Instagram appears to have reversed the changes to the API and multiple Instance users, including the developer, are reporting that photos uploaded using the app are sticking (i.e. not being deleted). This reversal of changes may be a temporary measure.
However, Windows Phone Developer Rudy Huyn, who is working on an Instagram app of his own, noted in a tweet that he had "hacked the new Instagram security", suggesting that even if Instagram does reinstate the API changes it will still be possible for third party apps to work around the new security measures.