Yes. Any member can reward or penalize any other member once per day. They're supposed to reward good, helpful answers, and moments when a member shows they've begun to figure out a tough problem after slight help. The negative ones are also useful -- they're supposed to highlight rule breakers: people who dump complete answers, people who ask in 'leet' speak, or insist all their work be done for them, etc. But everyone has their own criteria for their ratings.