I do believe in positive reinforcement. It works with kids, dogs and adults. However, adults are a bit smarter than dogs and most kids. I think giving out a trinket is a good idea and helps, but if it is not managed in the right way it just looks stupid and can feel a bit insulting because it feels like being treated like a child.
To me it's kind of like convincing people in church that if you behave, you will get this nice reward. That is more of a bribe to get people who otherwise might not do the right things to fall in line for a handout. Doesn't make them people who will naturally make the right choice every time unless they think someone (or God, or a supervisor...not to compare the two

) is watching.
What a management group should do for "real" and lasting culture change is treat people like adults. Include them in decision making even if it is on lower level items or empower them with desicion making abilities (at an appropriate responsibility level). Pay them. Reward them for going that extra mile to ensure a job goes right, but this should be a relatively rare occasion and for the things that are above and beyond. If you are treating people right and offering a nice package, you will end up recruiting good employees that do a good job for the sake of doing a good job and taking a little pride. You can't turn bad employee's into good ones with bribes. You can get them to behave to a certain degree, but a problem employee will eventually still be a problem employee if given the chance, and that is really important in our industry. What will a person do if no one is looking? That is called culture.
Sounds like a bandaid to me. It often times is a path a poor management group would take to avoid actually managing a problem.
I like reward systems if they applied correctly (most I have seen are not). Usually, if a management team is really amped up on a reward system, they are covering for their own deficiencies in the ability to manage the group.