Restaurants don't switch between miles and cashback! With a few exceptions (a handful of restaurants give miles to one airline but not another) he very same restaurants particpate in all the various incarnations of iDine. They give miles to people whose account is collecting miles, cashback to people whose account is collecting cashback.

So it's your account, not those restaurants, which switched. (Or at least the credit card you've been using switched, or you switched which credit card you were using without realizing it. Or one other possibilitiy is if your airline dropped iDine, then maybe iDine in THAT case switched you to cashback?)

Looking up Rochester in my (BA's EC Dining) version of iDine, I still see restaurants such as The Cartwright Inn, Casa D'amici, Comix Cafe, Crescent Beach Hotel, Critics On The Mall, Cutler's Restaurant (new), Davinci's (3 locations), Duels Cafe, Elmwood Inn, Empire State Brewing, etc, etc (ie, I only looked at the first two pages of the Buffalo/Rochester area and only looked for Rochester proper not suburbs) all still give 10 miles/$ in EC Dining, and undoubtedly most if not all of those give 10 miles/$ in all other airline programs that still participate in iDine. But since I have no idea which airline program you were in, I can't further explain why you think the restaurants switched on you...