I use three different accounts for downloading from the App Store, each in a different country.
When there is an update, I have to connect to the correct App Store to download the update, but sometimes I can't remeber from which store an app was downloaded and so I need to connect to each one in turns.
I would like to be able to find the account I used to download an app so that I can connect to the correct App Store immediately. Also, this would enable me to verify if the app already exists in the App Store of my main account and buy/download it from there.