Solution: 1cm or 3/8" wide strip from a pop/soda can, inserted into bottom of USB port to release connector!
Here's my story:
My wife and I each just purchased an iPhone 5, and both our USB cables have this defect (deep retent notches) resulting in a stuck cable in many USB ports. When my wife first reported the cable was stuck in her Acer notebook, I thought she wasn't tugging hard enough or simply needed to wiggle it out. I went to try it out and sure enough, it was stuck! Fortunately, I hadn't cracked my fingers and remarked, "Let me show you how it's done, Honey..." before attempting the extraction.
After inspecting the USB connector on some other devices (mouse, flash drives, etc.), I figured the retention tabs were not releasing from the lightning cable for some reason (at this point I didn't know why), so I used a thin piece of metal as a shim to release the retent tabs. Once extracted, I inserted the lightning cable's USB connector into other USB ports on the notebook and experienced the same problem.
I later inspected a spare lightning cable that a co-worker had purchased (i.e. it was not the one included with his iPhone 5), and it appears to have the same deep notches (and presumably the same experience in many USB ports).
I called Apple support and was surprised when the guy said he had never heard of this issue. He then asked his supervisor who also hadn't heard of this, and suggested that the notebook is probably too new and the USB ports hadn't been broken in yet (which is not the case; my wife's Acer is a couple years old now, and my Dell is (I'm almost embarrassed to say) around 8 years old).
Given that it's now November 8 that I'm writing this, and the original post was from late September, I'm surprised this isn't a "known issue" in Apple support circles. Anyway, he said they could ship me out a new cable, but would put a hold on my credit card until I shipped the old one back. I declined since he wasn't sure if the replacement cable would have this issue addressed, and I figured it's possibly pointless and a waste of time unless he was certain that the new cable would not suffer the same issue. How is everyone else's experience with replacement cables?
Anyway, he suggested I visit the Apple Store as an alternative, which I may do. Or do I wait for a recall? I wouldn't mind keeping this cable since it still works with the AC adapter cube that came with it (albeit quite tight), and figured that a free cable would be the least they could do for the nuissance caused. Fortunately no damage caused, but I was almost prepared to use brute force...
Ben