Sometimes you have to listen very closely when Steve Jobs promises something.

When Apple's (AAPL) CEO introduced movie rentals at Macworld two weeks ago, he demonstrated how films downloaded through iTunes could be sent with one click to an iPod, iPhone or iPod touch.

Then, according to my notes, he said something about "current generation iPods."

Those three words have got a lot of people on Apple's discussion boards hopping mad today. It turns out that fifth-generation video iPods purchased as recently as five months ago won't play those iTunes movie rentals — and not because of any hardware deficiency. Current generation iPods, per the footnote in Apple's press release here, include only the "iPod classic, iPod nano with video and iPod touch."

"This is bogus!!!!!" writes user ninzan on one of at least a half-dozen threads devoted to the topic. "I was all up on apple rental now that I find out that I have been locked out i feel like a moronic apple groupie. My 5g Ipod video is apparently too old and my new itouch did not come with video output. i'm screwed"

The only recourse, it seems, is to ask for your rental fee back. According to reader reports, Apple has started to issue refunds.

What's going on?

Bryan Gardiner at Wired called around and by yesterday had come up with several theories.

Forrester's James McQuivey thinks it may be a strategy of planned obsolescence — a ploy by Apple to get users to buy new iPods.

Yankee Group's Carl Howe thinks it might have something to do with the clock-resetting trick some users have discovered for extending the life of a 30-day, 24-hour rental.

The most plausible explanation, to my ear, comes from The Unofficial Apple Weblog's Christina Warren. She points out here that fifth-generation iPods had a simple analog video output feature (replaced with authentication chip-equipped composite and component AV on the classic, touch and nano with video) that would have allowed rented content to be easily copied. Closing this so-called video hole may have been a requirement imposed on Apple by the movie studios.

Of course, nobody bought a video iPod before September in order to play movies rented on iTunes — an option that didn't exist at the time. Still, for millions of video iPod owners (disclaimer: I'm one of them), it's annoying to be so close and yet so far. Clearer disclosure would have been nice. And a refund of a few bucks to users who rented before they discovered the fine print seems like the least Apple could do.

With less than two weeks to go before Steve Jobs' Jan. 15 keynote, analyst Shaw Wu of American Technology Research offers his best guess for what Apple's (AAPL) CEO might have up his sleeve at Macworld Expo 2008. In a note to clients issued this morning, Wu predicts:

• Blu-ray. Citing unnamed sources, Wu says that Apple will outline an HD strategy that backs Sony's Blu-ray format over the HD-DVD standard favored by Microsoft. (Although Wu hedges his bets and suggests that Apple might also use a combo Blu-ray/HD-DVD drive.)
• Subnotebook. Wu says Apple will re-enter the subnotebook space (nothing new there) but adds that Jobs may call the new machine the MacBook mini or MacBook slim. Any preferences?
• Movie rentals. Wu points out that the digital movie rental deals expected to be announced at Macworld are a departure driven by necessity, and represent a new business model for Apple. "Whether these movies expire based on time and/or usage is unclear to us," he writes, "But we do believe that rentals are a significant change in its philosophy."
• Speed bumps and external HDD: In the category of smaller announcements, Wu is picking up potential news related to speed bumps and or capacity bumps in current Macs and iPhones, and an external HDD storage/dock/streaming device for the Airport Extreme and the new MacBook mini/slim.
• Apple TV. Wu sees two big shortcomings in the current product: 1. no way to connect directly to the Internet for TV and movie content and 2. lack of a TV tuner. "Our sources indicate that AAPL is working on fixing these weaknesses to make Apple TV a much stronger product," he writes, later in 2008 or perhaps 2009, but not at Macworld 2008.
• 3G iPhone. Coming mid to second-half 2008 at a higher price point, Wu says, allowing Apple to reposition the current iPhone as a "more mainstream" product.

What does Apple (AAPL) have in store for Macworld? Four weeks before Steve Jobs' Jan. 15 keynote, Piper Jaffray analyst Gene Munster has offered his best guess. The report to clients he issued today hews pretty closely to conventional wisdom, but provides a handful of new details.

• Macintosh: Munster expects that in addition to updates across the Mac line Jobs will introduce that long-awaited thin Mac with an 11" to 13" screen, 64 GB of NAND-based solid state memory and (maybe) a iPhone-like multitouch touchpad. Price: somewhere between the $1,099 MacBook and the $1,999 MacBook Pro.
• iPhone: Apple could up the storage to 16 GB while maintaining the $399 price point, but it's too early for the 3G iPhone 2, says Munster. He now expects that phone in May or June 2008 (His earlier predictions had pegged it for sometime between Sept. and Nov.)
• iTunes: "We also expect Apple to announce new content partnerships with one or more movie studios, which may involve the launch of iTunes movie rentals," Munster writes. "We believe there is a 50% chance the download service is announced at Macworld, and a 90% chance by mid 2008."

Meanwhile, UBS analyst Ben Reitzes has issued a bullish report based on a survey of more than 30 stores in which his research team found Mac demand "outpacing prior expectations."

"Even with prospects for a slowing economy," he writes, "we believe Mac demand can keep going strong with new products that we have detected in the supply chain. Given higher margins for the 'Mac ecosystem,' including software – we are raising estimates."

For more on the UBS report, see AppleInsider here.