AA battery powered mp3 player?

“But I doubt you’re ever very far away from an AC outlet to plug in a charger?”

it is not about being far from an outlet for a long time, but remembering to recharge a player with a built in battery when it needs it, and leaving enough time to do so. Some chargers will charge up to 4 AA batteries in just 15 minutes.

“but even then you can carry a USB charging device powered by . . . yep, your AA batteries.”

That seems very annoying. One would need 4 AA batteries to reach around 5 volts. If one could power the player from an external battery pack it wouldn’t be so bad, but charging the internal battery from an external battery pack does not seem like a desirable thing to do.

“I don’t buy this as an oversight on SanDisk’s part. A firmware boo-boo? Definitely!”

Not really, as a 4000 or so song limit seems reasonable when the player can’t hold more than 16 gigs, since most people use a bitrate of at least 128 kbps for their music. Having a 4000 or so song limit when 16 gig micro SD cards are available though, and the player could have 24 gigs of storage is not a good thing.

"Besides, they (SanDisk) knew going into this realm that with the SDHC micro-card the possible near-future total memory capacity would be 40GB (8GB on-board & 32GB SDHC card). "

They also knew they would have firmware updates before then.

“They should have planned (key word: planned) for it regardless!”

They did plan for it, they planned future firmware updates.  Since they are a leading maker of micro SD cards, they know exactly when certain capacity cards will be available.