I recently talked about this, so when I saw this post on the importance of authenticity in green marketing from No Impact Man, I want to pass it along. Like I said--only promise what you're planning to deliver (and what you actually can deliver). Anything else will expose you (or those you are planning the event for) as a fraud and strip you (AND your clients) of credibility. Don't think you won't be found out and don't think others won't spread the word.
Here is a another great post on greenwashing from Joel Makower. The results of the study he discusses are unfortunate (though not surprising) and the first commenter mentions the famed "snake oil salesman." I don't sell products (at least not the type you buy in a big box store), but if I did, I would see opportunity here and that translates to what we do as event planners, too. If someone else is cheating (even the slightest cheat opens the door to suspicion), and found out they will be--by an outstanding group of bloggers growing in numbers almost by the day), your honest practices--even if you can't promise everything the greenwashers did--will shine. The "snake oil" tactics only worked in an "informationless" world. Today, those salesmen would be hard-pressed to make a second sale.
P.S. I am kicking myself because sometime this week I read about a study that showed that green blogs are growing at a rapid rate and a significant percentage of those blogs are focused on exposing green shams. Of course, I cannot seem to find it. If I do, I will post it.