Samsung may have dug in its heels and refused to carrier-customize the Galaxy S III in the US, but differences in availability of the free 48GB Dropbox promotion show not all phones are created equal. While two years of free storage through Dropbox was announced alongside the Galaxy S III originally, it seems not all carriers have decided to take part. "Select carriers have opted-out of the promotion on phones otherwise eligible" Dropbox writes in its customer support pages on the promotion. "Unfortunately, AT&T and Verizon are among these carriers not currently participating."
In Europe, where the Galaxy S III has already gone on sale, those signing up to Dropbox via the app pre-loaded onto the phone get 48GB of extra space above and beyond the free space the cloud storage service typically offers. That can amount to as much as 66GB.
However, in the US, while the Galaxy S III will be available across five carriers, the two largest - AT&T and Verizon - won't be taking part in the Dropbox scheme. It's unclear as to the reasons why both have opted out, though it's possible that one or both is planning its own cloud alternative.
It's also worth noting that the promotion doesn't necessarily last for two years, at least not with the full 48GB. While Samsung initially announced a deal where users would get 48GB for the typical length of a new phone contract - 24 months - the help pages also confirm that there is a second, less generous version of the promotion.
That version offers 48GB for the first twelve months, but then scales that back to 3GB on top of the free allowance for a subsequent twelve months. Update: We're told that all versions of the Galaxy S III sold in the US that are eligible for the Dropbox offer will get 48GB for the full two years.
[Thanks to everyone who sent this in!]