We just received a tip from a reader that Google is beginning to send out emails to Google Play customers who ordered its new Nexus 4 device to inform them the device is currently on backorder. As you can see in the email above, Google expects to ship the device “within three weeks,” and it will credit customers who have to wait with the shipping charges. Google cited “overwhelming demand” as the reason for the delays. We previously reported that initial supplies of the device sold out within minutes of officially going on sale in the U.S. earlier this week.