As the editor CruiseMates I spent about three hours one day updating cruise line information for them. I am considered an "expert" in the field by many people.
Well, some IDIOT editor at Wikipedia said I could not contribute to their site because it was self promotion - that I was promoting myself as an expert. They took down every single word I wrote.
In other words, if you are qualified to add content to Wikipedia you are not allowed to do so. I was so mad I will never, ever try to help Wikipedia ever again.
That was just a plain insult to my time and intelligence, and a stupid, stupid rule. Why was that guy allowed to tell me what can be said about cruises in Wikipedia? He doesn't know anything about cruises, and he had no idea how valuable and unique my contribution was - because he knows nothiing about my field. Their loss and yours.