In what appears with the regularity of New Year's Eve, Christmas and my birthday, Mac tablet rumors are again making headlines.

The enormous success of the iPhone and the iPod touch, though, might lend some credence this go around. Or we might keep on chasing the same dream just as speculation begins heating up about the soon-to-be approaching holiday shopping season.

The new ingredients this time are the reliability and popularity of Apple's touch screens, the emergence of Amazon's Kindle as a bestseller and the increasing number of tiny netbooks finding their way to market. Stir in the soon-to-expire iPhone exclusivity contract with AT&T and rumors of Apple cozying up to Verizon, and you have the latest iteration of a long-standing dream. A Mac you can tote around, with a little something beyond MacBook Air in the gee-whiz factor, and someone like Verizon helping to foot the hardware bill.

Most commonly described as something akin to an oversized iPod Touch, the general size of this rumored product is usually around nine to ten inches. Sometimes a real keyboard is thrown in as part of the mix, but most speculative images feature some kind of on-screen touch keyboard.

And we've seen these sketches and these mockups again and again. The Street even claims that Apple's had a working prototype for over a year, though the total lack of leaked photos makes that tale hard to credit.  Even for Apple with its high level of security.

This much is true: Apple addicts and tech journalists will continue to salivate over the potential for a Mac tablet and continue to speculate and spin stories and maybe some day, at long last, they'll be right.