Apple has introduced a new token called SetActiviationToken that's required to connect to Siri. That means that Siri won't work on older phones using third-party apps like Spire, or any other Siri hacks. (iDownload Blog posted the video below, which shows the issue in action.) Luckily for everyone using a port, it seems that the masses have already figured out a workaround:
In order to remedy the issue, purge the com.apple.assistant.plist file (var > mobile > Library > Preferences). Many comments on Twitter and on various news outlets suggest this has worked pretty well.
If that particular workaround doesn't work, hackers will doubtless soon figure out another way to get Siri off the iPhone 4S and onto other devices. It's just unfortunate that Apple appears to have no plans to loosen its grip. [CNET]