Re: Is there a way for Amazon to link accounts via iOS App using same iTunes ID?
Apps can read a lot of the data on the device. Some more than others.
Bottom line is, regardless of OS, be it iOS or Android, and regardless of iTunes ID/other information, the most crucial info used (I would assume) with linking is 'Unique Device Identification Number'. As the name suggests, its a unique number per device. If two Amazon accounts selling similar items are using the same UDI number, its an easy link.
Like I said above, Amazon apps probably use this feature, most other apps certainly do, i.e. those which dish out special offers to ensure you dont abuse it by reinstalling the apps (McDonalds).
Best way around it is to use the mobile browser to access the Amazon account, that way you prevent yourself from getting linked.
P.S. Apps can read a lot, contacts, calendars, etc. they could use this information to link accounts - you would need to grant the app permission to access such sensitive information though.
Hope that helps :) | 
