When Apple (NASDAQ:AAPL) unveiled its new iPad, there was one feature many analysts had been expecting that was missing: Siri. Apple’s voice recognition system, and one of Apple’s key promotional points for the iPhone 4S, was conspicuous in its absence.

The fact that not all iPads always have Internet connectivity (required for Siri, which communicates with Apple servers in order to formulate responses) is one reason why Apple may have chosen to skip Siri implementation. It’s also still a beta product, so Apple may be keeping its availability restricted to a control group — iPhone 4S owners — for now.

Cult of Mac‘s John Brownlee recently posted the reason why he believes it’s missing. According to Brownlee, Siri is broken. He contends that Apple’s system is “quantifiably dumber, less intelligent and less useful than it was just five months ago when it first launched.” The reason? Brownlee’s theory is that unexpected demand from iPhone 4S users is overloading Apple servers, forcing the company to allocate fewer processing cycles per Siri query, resulting in less-accurate responses.

Woz weighs in

Apple cofounder Steve Wozniak has gone on record with his disappointment in Siri, which he says is less accurate now than when it was available as a standalone service (prior to being purchased by Apple). And in recent news, a lawsuit was filed against Apple by an iPhone 4S user who claims Siri is far less useful than Apple depicts in its advertising.

If Cult of Mac is correct that Siri’s apparent degradation is a result of server overload, then it’s not unreasonable to think that sales of the new iPad would have added sufficient new Siri users to put further stress on the system — which would not be a good thing. Apple became the butt of jokes 20 years ago when it released the Newton PDA with handwriting recognition, only to have the feature perform so poorly that it was widely ridiculed (becoming a pop culture symbol of technology failure) and one of the first products Steve Jobs killed on his return to the company. Apple does not want a repeat of the Newton handwriting fiasco.

Apple engineers are undoubtedly working around the clock on Siri. With Google (NASDAQ:GOOG) reportedly working on “Assistant,” an advanced voice recognition system for Android, there’s even more pressure to get it right.

As of this writing, Brad Moon did not own a position in any of the stocks named here.