I was able to get a couple of specials honored in SF (buy one get one drinks in both cases). Recently I've seem some of the specials requiring an AMEX credit c

I was able to get a couple of specials honored in SF (buy one get one drinks in both cases). Recently I've seem some of the specials requiring an AMEX credit card linked to my foursquare account, which I feel crosses the "worth it" line.