How often do you say ‘thank you’?

One of the important things of being a project manager, at least a certified project manager through PMI, means imbibing the code of ethics. Code of ethics mandates PMs to acknowledge and give credit where it's due. Every time you renew your certification you *have* to renew the code of ethics, barring nothing. Given this, it is important to say "thank you" symbolically, verbally, gesturally and any other way you can. I try my best to keep the acknowledgements in track, whether it be a presentation where I have to "borrow" pictures from somewhere or call out the contribution of a fellow worker.

I feel, even outside of being a PM, a thank you as an acknowledgement, appreciation goes a very long way in building great teams, fosters trust and healthy and long lasting relationships, and communication channels which don't disappear overnight. Thank early, thank often, but don't overdo it. It sends wrong messages.

Absolutely. All the time. Whether we are speaking of ethics or just plain good manners and respect, the words thank you [and please] are and should be 'standard'.

I agree with Andrew Craig.
Gratitude is the best attitude.

Thank you is a very simple word but could mean a lot to someone. It is very important to show appreciation even if by saying acqord as simple as thank you.

It shows your appreciation for something! In practice I always thank my team and my customers. I do see a difference with the younger people who are coming into the workforce though. It seems that "Thank you" isn't as natural of a word to say. I use it all the time. If my team knows I appreciate the work they do, they do more!