If and when I see signs of behavior I consider simply unbecoming to agents, I generally ignore it. While it may disappoint me, if it does not pose a direct threat or danger to a consumer, I will not take any action. It is rare that I pick up the phone and call another broker to discuss an issue, but there is reason to so on occasion.
Frankly, I get annoyed at petty reporting of minor infractions. For example, I have witnessed a broker calling the police station to report the fact a competing broker placed a direction sign on a street corner in a municipality where such was probated. I haven't the time or inclination to participate in this nonsense activity.
Actions which are clearly illegal or pose danger to the public should be reported. Serious issues would justify a report made to the real estate commission.
I am an advocate of trying to resolve things directly and at a lower level first. Difficulties can arise from failed expectations and breakdown in communications. The first attempt at resolution should be with the agent or his/her broker. I have seen some posts on Trulia where the RE Pro recommended a report to a board attorney, an association or real estate commission. I have considered some of these recommendations unfounded based upon the limited info presented by the poster. Instead of bogging systems down unnecessarily, I recommend finding out more about the root of the problem. So often communication can go a long way in resolving a misinterpretation. A misunderstanding might be rectified in an afternoon absent the aggravation and time investment of escalation if not needed.
Unfortunately, in this, as in any industry, you will find those who are less scrupulous than others. I believe in recommending appropriate action based upon the infraction. Serious issues do belong at a high level, and perhaps directly to that level. The first course of action in most cases should be to contact the broker. Most brokers will make a serious effort. If that does not bring about resolution, contact the local board.