Well, I don't want to get into the matter too much, since it is not a problem (and I don't want to talk about piracy)
but there is an app in the Italian marketplace developed by my carrier, which app isn't obviously available outside the Italian marketplace.
I was able to download it and install it by searching for it through the phone marketplace. But the same app isn't visible on the windowsphone.com marketplace.
When I search for it I get as a suggestion, on the auto-complete list, the name of the app. But then as soon as I open it, the page says that it couldn't find the app.
It is really intriguing.