If you have a Windows Phone bound to a specific Microsoft account, the first time you open Marketplace – and usually only then (at least until Microsoft [re-]introduces geographical profile migrations) – you can specify the country that you purchase apps from, and provided that you haven’t used XBox Live or Zune until then, you will also get an XBox Live gamertag created at the same time (previously also referred to as a Zune account, in some conditions): an informational message will tell you about it (indicating that your initial profile would be named something like Player######), but you might easily forget about this as at that time you were planning to just get some Windows Phone apps from the store, and cared a lot less about playing XBox Live games or anything else.
At first thought, this shouldn’t be an issue, as you could open XBox Live Web site or Phone app, or download your profile on an XBox console later, and the gamertag will be still there waiting for you, although automatically bound to the same country originally selected for the Windows Phone Marketplace.
But the big annoyance may strike after some other while: after 30 days since you’ve downloaded an XBox Live profile on a physical XBox console, you would be able to move the gamertag to a different Microsoft account. That’s nice (especially as it could technically help you get rid of a gamertag with a wrong country selection, such as if you moved away to another region of the World or if you made a selection mistake), but as soon as you’ll try to open Marketplace again on your Windows Phone – after allowing you to select a country again – you’ll notice that your previous purchase history would be missing; the previously downloaded apps would be still available on the phone, but you won’t get automatic updates for them anymore and you won’t be able to reinstall them if you deleted them without purchasing them again, as the history itself is recorded (and moved away!) – hold your breath – together with the (logically) unrelated XBox gamertag!
This is exceptionally stupid (I’m still in denial, thinking about it!), considering that generally – at least in my opinion – Microsoft products and services were always logically consistent, proving deep architectural understanding and therefore being driven by great design decisions. Not this time.
(One might argue that XBox gamertags must be related to Windows Phone Marketplace because phone apps and games are available from the same store, and that historical reasons promoted XBox profiles as the best candidates for being used as marketplace accounts too, but considering that XBox consoles are only for games while Windows Phone apps are more generic, I’m not going to accept these excuses as plausible, although generally I’m in favor of all logical unification propositions: sorry; the possible annoyance generated by the current situation described above is too big!)
Note: The issue doesn’t affect Windows 8 (PC) apps and settings – it seems that the lesson has been learned – but still, Windows Phone 8 seems to follow the same Zune path (as Microsoft focused more in other directions with its new mobile platform version), so be careful!