1script - 4:19 pm on Aug 21, 2013 (gmt 0)
I get a feeling that Amazon would love to simply drop their affiliate program altogether but are reluctant to do so just yet. Perhaps considering a possible PR backlash, perhaps because sales through affiliates still account for several % of the total they don't want gone yet - who knows? Not allowing mobile would create a great way to lose affiliates gradually, without raising any red flags, as the total % of mobile traffic grows.
I would venture a guess that since last year, as Amazon host crowding in Google SERPs shot up to ridiculous heights (and is probably coming again this shopping season), they see no reason for the small but cumbersome marketing channel that affiliates are. It's much easier for Jeff to play golf with Larry and agree that G gives A free reign of the first 2 pages of SERPs (and perhaps get some cut - why not?) than to deal with 1000s of individual affiliates, 1099s, EBTs, ToS and DMCA compliance etc.
That said, are you sure this is about mobile Web and not mobile app traffic? I have to admit this is a news to me - any chance to post a relevant quote from the ToS?