It is sold out at Amazon. It is sold out at Best Buy online. It is sold out at the 16 Best Buy stores closest to my home in North Carolina. The nearest Best Buy availability is in Roanoke, Va. (Amazon and Best Buy are the retail outlets sanctioned by Google.) You can buy it directly from Google at the Play Store, but as of this writing, the wait time for shipping has been extended to three to four weeks.
In a world where people line up for hours to buy a $500 tablet, selling out a $35 dongle isn't necessarily a milestone, or an indicator of anything signific