Negative experiences can be discussed but it must be done with care. There are two sides to every story and if the other side does not have a chance to share their side, you will never know what really happened. As we all know, most often when one hears both sides of a story, the story is normally quite different than first presented.
Further, Cloudy Nights is a big site, clearly big enough that it is attractive to vendors and so it faces some unique problems.
For example, vendors have been known to register under false names and the make negative comments about their competitors products, vendors have been known to register under false names and make positive comments about their own products. Cloudy nights has to be vigilent about such practices and has instituted measures to try to control them.
In sharing one's experiences, particularly ones that did not go so well, here are some don'ts and do's:
1. Don't bring anger and frustration to any vendor discussion, one needs to be calm and rational.
2. Don't plan on initiating a post about a bad experience. One reason the TOS clearly states that CN is not a place to air vendor complaints is because it does not want to be used as leverage by a customer in dealing unfairly with a vendor. As probably the largest online astronomy site, CN does not want customers threatening vendors with "if you don't do as I want, I will post it on CN".
3. Don't Hijack a thread. If someone is discussing a bad experience with vendor X, don't bring up your bad experience with vendor Y. It is off topic and irrelevent.
4. Do respond when it is appropriate to the thread. If Joe is considering buying from Vendor X and you were dissatified with a transaction, urge that Joe looks a little closer and share what happened to you and why you were dissappointed.
5. Do stick to the facts, don't call Vendor X a cheat or dishonest or add malice and forethought. Just explain the events as best you can and leave it at that. Anger and name calling have no place in any thread on CN.
6. A calm cool post is far more effective in communicating dissatifaction than venting and hitting the wall. It provides solid information about your concerns...
7. Do share your concerns. Your emotion should be concern for the original poster. "I am concerned about your interest in Vendor X. Last year I ordered a telescope from them and was promised that it would be delivered in 1 month. I have waited for nearly a year and it still has not been delivered, from the companies website it seems clear that it will still be quite a while longer, so far, none of these have been delivered.
Now I see you are interested in this same scope. Please be aware of the delay in delivery as well as some other quality issues that have arisen during the past year..."
As I said, discussing negative experiences is possible but it must be done with care and caution. It is too easy to forget the intent and get tangled up in justifying old anger and frustration...
...which benefits no one. Not yourself, nor the prospective customer, nor the vendor.