The question "Is Snow Leopard retired?" went legitimate as soon as last week.

That's because Apple has always dropped security update support for one edition around the time it has two newer in play. If the current OS X is dubbed "n," then "n-2" support ends at the debut of "n."

In other words, patches are provided only to the newest OS X and the one immediately preceding it. With Mountain Lion's debut last Wednesday, that informal policy -- Apple has never put its support practices on paper or its website -- means the two editions that will receive patches are OS X 10.7, aka 2011's Lion, and the brand new 10.8, or Mountain Lion.

Apple last shipped a Snow Leopard security update in May 2012.

"I would expect that Snow Leopard is toast," said Chet Wisniewski, senior security adviser at Sophos, when asked today of his expectations. "They seem to apply that 'n-2' rule [of no security updates] somewhat universally, even when it doesn't make sense."