Steve Jobs famously said that great artists steal, and the company has often taken that mantra to the extreme over the years. Some would say that much of Apple’s current software bears more than a passing resemblance to some of its competitors’ products.

Take iOS 5’s Notification Center, for example. You’d need to be blind to say that it does not look eerily similar to the same notification system that Android has packed since day one. Some would argue that there are only so many ways you can handle something like a pull-down notification window. Some would call it stealing.

Apple has even taken some cues from its own App Store. Mobile Safari now sports a “Reading List” feature that offers a similar service to that of Instapaper, the famous web app that also has a popular iOS app in the App Store. Instapaper’s developer, Marco Arment, doesn’t seem too concerned, but others were not so happy…

With Apple’s history of taking features from the very developers who make the App Store so strong, I got to wondering about what app could be next.

One app that may be a little concerned is Instagram. Already hugely popular amongst iOS users – and iOS users only, no Android version here – Instagram’s biggest draw is the way it can add filters and boarders to our photos before sharing them in a photo-only social network. It seems that people really enjoy turning highly detailed photos into something that resembles a Polaroid shot from the 1980s.

Apple has already added a HDR feature to its Camera apps. It is, theoretically, a small step from there to adding a selection of filters that could be applied when taking a photo, ready to be shared on Twitter or Facebook.

Many will be reading this and shouting at their screens. “But it’s the social aspect that makes Instagram special!” you’re all declaring, and I’d agree. But if you can instantly upload images to Twitter (or Facebook, if iOS 6 adds integrated Facebook support, just as iOS 5 added Twitter) from inside the Camera app, do you really need another social network?

Apple has already proven that people will use its built-in features instead of third-party apps when given the choice. We’d wager that HDR apps don’t do so well now that their big feature is part of iOS itself. It may not be the best HDR out there, but it’s the one that’s attached to the Camera app that is front and center on all iOS devices. It’s the one people use.

Who knows, Apple may even decide to make its own photo network, but we all know how its effort at a music network turned out with Ping, don’t we?

It’s not just Instagram that should be worried, either. Proper podcast handling in the Music app would negate the need for specialised podcasting apps like Instacast. Would you use a third-party instant messaging app if Apple bundled its own? You already don’t need to because we have iMessage.

Apple must be careful. If it continues to borrow/steal/liberate features from App Store apps it risks alienating the very developers who have made the iOS platform so strong over the years. Those huge app figures and download numbers Apple likes to tout at its media events? Third-party app developers make that happen.