At foxwoods there were several times I was doing pretty well in Sp21 and some asian people starting backbetting me because they saw that I was "lucky". Then, they got pissed when I was doing some of the non-obvious (but still correct) Sp21 B.S. and index plays. Since they are so much less obvious than in blackjack (such as when I hit a 14v5), I've found people at tables to get even more pissed, especially when they back-bet me. So then someone backbet me I just gave them a warning that "sometimes I play a little risky!" not for their benefit, but just so I don't have to hear them complain if I lose while making the correct play.