I lived in Russia for 2 years as a foreigner. I never noticed and issue with smiling. I think it has more to do with how much of an accent you have when speaking Russian and what you wear. If you are in a tourist area you have to be double aware (especially for little gypsy kids swarming you and pickpocketing). In the tourist areas taxis drivers try to rip you off. I remember an incident where they quoted a price that was really high. I just laughed and started walking away saying I'm not paying more than (1/10th the original price). He promptly agreed without hesitation.