If you scoffed at the news that Apple's Siri would only be available on the iPhone 4S, thinking that you could just use the standard Siri app that was still available on the App Store, then scoff no more. The freely available Siri app has been removed from the App Store completely, and as TechCrunch reports, the whole service is being taken down in advance of the official debut of the app as part of iOS 5. TUAW reader Luc reports that the current app now gives a note as it starts up that the app will be "leaving for home" on October 15th, so you have until then to enjoy the app as is if you happen to still have it installed. Presumably at that point, the old service will end, and you'll have to buy an iPhone 4S if you want access to the new service.
This basically makes sense: Apple's trying to sell devices, and it wouldn't really work to have a version of the service out there running around for free, even if that service isn't as integrated. Apple's done the same thing with other companies they've picked up and made official, including CoverFlow back in the day.
Unfortunately, if you're currently a big Siri user, then you'll have to upgrade your handset to keep using the service as is -- there is no built-in plan to let you keep using the current app.