The hearts of more than a few Verizon subscribers skipped a beat Thursday with a rumor out of Taiwan that Apple (AAPL) had ordered a huge number of iPhones equipped with CDMA modems — the cellular technology supported by Verizon’s (VZ) network.

AT&T (T) and most overseas carriers use an incompatible technology called GSM that drives Apple’s current crop of iPhones and G3 iPads.

The latest Verizon iPhone rumor, reported by Taipei-based Digitimes and picked up by a handful of U.S.-based blogs, seemed to attach a number — 10 million units — to the
Wall Street Journal
‘s report last March that Pegatron Technology Corp., a subsidiary of Taiwan’s ASUSTeK Computer, was building a CDMA iPhone for Apple, with mass production scheduled to begin in September.

But a few caveats are in order. 

First, what Digitimes actually wrote was that “annual shipments [are] expected to reach 10 million units” — without specifying when they might reach that target.

Second, Digitimes reported that Apple’s order should start contributing to Pegatron’s revenues in August or September, leaving open the question of when finished phones would actually hit the U.S. market.

Third, there’s the deepening mystery of when Apple’s exclusive iPhone contract with AT&T expires. The latest twist is a report in Engadget that suggests that it was originally scheduled to run to 2012, although the terms may have since been altered.

Finally, consider the source. Although Digitimes is closely read by Western reporters, its track record is mixed at best. Three years ago, MacRumors‘ editor Arnold Kim briefly stopped linking to Digitimes because the accuracy of its reports over a 5-year period (14 rumors total. 1 True. 10 Wrong. 2 Possible. 1 Unknown) was so poor.

As an AT&T spokesperson told the Journal last March: “There has been lots of incorrect speculation on CDMA iPhones for a long time. We haven’t seen one yet and only Apple knows when that might occur.”

See also:

• Casting doubt on Verizon iPhone rumor
• Apple surges on Verizon iPhone report
• Next year’s iPhone
• Verizon iPhone unveiling next week? Not.

[Follow Philip Elmer-DeWitt on Twitter @philiped]