Interesting thought. The most customer friedly solution I could image would be a 'iTunes Match' like service for Apps. While seting up your Windows Phone, they

Interesting thought. The most customer friedly solution I could image would be a 'iTunes Match' like service for Apps. While seting up your Windows Phone, they could ask for your iTunes or Android Marketplace credentials and scan these accounts for past purchases of popular apps also available for Windows Phone and mark them as purchased in the Windows Phone App Marketplace.