Promoting your website on a Page's Wall/Discussions Board

I think this is just like standard forums, it all depends on the relevance of your promoting. Why not try and engage yourself in a way that positions you as an authority on the subject and build up a rapport with the other users first? You might even be able to get the page owners to link to your site or talk about it if you are helpful enough.

Thanks mate

I don't think it's a bad etiquette. I do it sometimes, but only at my own personal facebook account where my friends can view it if they are interested. Posting on the wall of a popular page may not be unethical as well, just as long as you are promoting a good, informative, and educational site where the viewers can gain good things, not bad, especially for the very young ones. They are the most who are fond of facebook thingy. :-)

One man's spam is another man's dinner!

I'd find it tiresome if it's regular self promo, and i've seen some people do that.

Engaging has to be part of it or it won't have any long term value.