It is as you and
sdsearch say - exactly! In the areas I dine primarily, there have always been restaurants that do not participate every day. It's always wise to check the limitations before booking - the limit can even be one dine a month, specific days excluded, or even specific days only excluded (e.g. Mother's Day). And of course, some may accept a variety of credit cards - but not award miles on all the cards they accept. Caveat muncher.
The title has been edited to reflect the realities of Rewards Network - nothing new here, folks, move on... 
- Moderator
Originally Posted by
Points Scrounger
Ummmm .... perhaps all of the restaurants you frequent have been without blackout days, but I assure the option has existed all along. There is nothing "new" about it, except the way that information is displayed.