Apple Inc. (Nasdaq: AAPL) disappointed a lot of its fans when it failed to deliver the iPhone 5 yesterday. Then it did something worse: It made a lot of iPhone users mad by pulling a popular app -- and then bringing it back in an exclusive format.

It turns out that the voice recognition software on the new iPhone 4S, called Siri, used to be a popular third-party app, until it was pulled... and then brought back to life as an exclusive 4S feature.

As one woman complained to IU, "It's just really messed up. Apple used us as beta testers. It sucked all the ideas it could out of us, used our feedback to perfect its product, and then it gave us all a collective kick in the behinds."

In its first product announcement since former Apple CEO and founder Steve Jobs resigned, Apple unveiled an upgraded version of its existing handset: essentially a slightly smarter version of the same smartphone. It will be faster than the iPhone 4, Apple claims.

The product announcement underwhelmed a bit, as tech pundits complained they expected a full-blown iPhone 5. The stock price traded down $7 at one point -- though it rebounded with a market rally late in the day.

With the stock down and annoyance up, it wasn't the best day for the company that prides itself on being in touch with its customers. Could the absence of Jobs already be taking a toll after less than two months? It's probably too early to tell, but the Siri story shows how even Apple can anger its fan base.

At the product announcement yesterday, Apple execs showed how users can transform Siri to their own personal assistant. She can answer questions about anything from the weather to the meaning of a word, or find restaurants, make book reservations, or schedule appointments.

But a lot of iPhone users were far from impressed. Siri has been around the block a few times already: If she were a car, she'd have a lot of miles on the odometer.

Before Apple tried to pass off Siri as a key element of an updated operating system, Siri was a third-party app. As Techcrunch recalled in a post last night, "It wasn't as pretty, and not nearly as well integrated, but it had one big advantage: it ran on just about any iOS device."

More than a year ago, Apple bought Siri. The app remained, living on without updates. Then, sometime last summer, it vanished from the App Store. Users who had her could keep her, but it was no longer possible to download Siri.

Apparently Apple had enough unpaid market researchers on its team, using the app, posting feedback, and offering suggestions on how to make it even more appealing, efficient, and convenient. App users said they never got any payback for their comments: no updates, no new versions.

Ah, but one was in development... for exclusive use on the iPhone 4S.

Shortly after Apple announced the role Siri would play on the iPhone 4S, the company shut down the servers for the existing Siri app. And on a night Apple aficionados expected to be oohing and aahing over the next-generation iPhone, they were left instead to ponder a disturbing development.

What kind of company laughs at its customers by taking away something they already had for free, to market it as a hot feature on an upgraded phone? In conversations across the blogosphere, in Tweets, and in wall posts, iPhone users lamented the unknowable.

What happened to Siri?

The short answer -- as some existing iPhone users discovered through a cryptic mid-evening message on their phones -- is that Siri is leaving. The app stopped working around the time of the product announcement.

Several hours later, some users reported getting Siri back. Apparently, at least some of the servers were turned back on.

However, users also got a warning that time was running out. When the app was restored, it came back with the message, "I've been replaced! The new Siri is even smarter and better looking than me, and waiting for you on the iPhone 4S. I'll be leaving for home Oct 15th. Until then... how can I help you?"

Last night, a lot of iPhone users were asking for help with the same thing. But it's doubtful Siri will be able to answer this time. "What I want to know," an iPhone 4 customer explained to IU, "is this. How can I keep using Siri without getting a new phone?"