Dear Aunt TUAW,
Why can't I have Siri on my computer? My laptop has a mic and while its not as new as a 4S its still gotta have more horsepower and bandwidth, yes?
Seriously, more opportunities to use it can only help Apple.
Your loving nephew,
As for Siri on computers, yes, there's no technological limitations as to why the service could not be deployed to Macs and PCs. After all, Dragon Dictation / Nuance does.
The reason is more likely limited to the following factors. First, Siri currently defines Apple's flagship product, the iPhone 4S. It's exclusive to that platform and is rolling out slowly to additional languages and countries.
Second, Siri is already encountering occasional service interruptions. That might be due to load (which would require scaling) or initial rollout quirks. Either way, Apple is unlikely to extend the service to desktops until those issues have been resolved.
Finally, Siri's strength lies less in its voice interpretation (which is superb, but so is a lot of the Dragon technology), but in its OS integration. Siri ties in directly to the address book, to the reminders app, to your calendar, and so forth. To move to the desktop, Apple would have to re-engineer major portions of its operating system to support this kind of tight Siri integration.
So will we see Siri on your computer? Auntie thinks "yes." Will we see it soon? Unlikely.