So, good observation in the abstract, but:
1) you're responding to someone who said "some jurisdictions"
2) siavosh's Twitter profile suggests that they're in San Francisco.
While it's true that it may not be a legal requirement (in some jurisdictions) to post a privacy policy, it's probably not a good idea to trust a service without one, particularly if said service is designed for posting potentially private personal information.
In other words: They should post a privacy policy - not because it's a legal requirement (though it may be) - but because it's good business. And no one will trust them otherwise.
Serious question: Do people treat privacy policies any different than EULA's? (To wit: Abstruse legalese that doesn't really tell anyone anything?)
I can summarize 95% of privacy policies right here:
* We won't sell your info (directly)
* We "may" provide your info to third parties based on ill-defined criterion
* We can change this at any time without telling you first
* If we get bought (which is likely), this is all rendered invalid
* If we break our word here, your recourse is precisely jack
If any user of the service is in California, then the state can potentially take legal action against you.
Whether this really matters to a particular company depends on where they are, but full-faith-and-credit means that at a minimum anyone based in the US has to worry about it.
Has the State of California ever taken legal action against any company located outside of CA for not complying with this regulation or is it just another one of those laws that are on the book but are never enforced?
One of the best "features" of the internet is that it is jurisdictionally grey.
Otherwise, why not just subject the entire world to the stringent requirements of China?