This is by invite only, just like they typically are. Check your groupons if you haven't. This seems like many others that have been posted but for May.
I saw the ones in April had negative ratings but the ones in March had positive? If this is something I shouldn't post in the future, let me know. To me, I sometimes mass delete the 5-10 Groupon/LivingSocial emails I get each day, so being reminded to take a closer look can be useful.
Link is for reference as it is invite only: