It works, tried it myself and there is about 20 positive DP on my blog/twitter as well. As long as you log in to Groupon and then click shop now on facebook it will work. You should also then be able to trigger a portal/Dans link and complete your purchase as well
Asking about the link on DD that doesn't require FB.
Tried in Incognito and it worked for me and JJ, just wanted more DP.