each download may take a period ranging from twenty to seventy minutes if you are connected to a wi-fi hotspot. If you use a 3G connection, instead, the download is inhibited and a message warns you that, due to the excessive size of the file, you must be connected to a wi-fi to continue to the download. Apart from the frustration generated by waiting too long for the completion of the download (especially if you consider that there are an infinite number of alternative sources of information available in a few seconds, for free, just surfing the web), when the user doesn’t have access to a wi-fi network, he is likely to quit the purchase altogether