I've eaten octopus in Greece and maybe elsewhere near the Mediterranean, and I suppose I've eaten it in the US in sushi and Mexican seafood cocktails, but recently I've noticed a number of people mentioning eating it as a main course or appetizer here in the US, including right here in my very much landlocked non-seafood-centric city. Is octopus a trendy food at the moment? I certainly wouldn't be surprised, as it can be quite tasty if prepared well. And if in the past 20 years or so we Americans have learned to love squid (so long as it's labeled "calamari" on the menu), then it makes sense we would venture on to octopus (and maybe cuttlefish is next).
I raise an eyebrow when I see a seafood that seems to be trendy because I am concerned about sustainability. But it looks to me like Monterey Bay Seafood Watch considers octopus from Hawaii and the Gulf of California sustainable.