Some days Lejocelyn added a feature request about Domains on OmegaWiki. Being one of those points that are also most relevant to me personally of course I answered. Why domains are so relevant? Well: let's say we have 1.000.000 expressions for English-German for a translator, but for us only a certain set of data is relevant when we do translations, so having all 1.000.000 Expressions to search, with all potential results in our glossary window is some kind of an overkill and instead of helping you to find the right term it would take you the triple of the time you need to look things up in a dictionary (let's say about physics or medicine).
Dictionaries are general, yes, but then the amount of specialistic terminology is limited to what is most often used, therefore each of us still has these very special dictionaries about just one topic and these are our most valuable tools besides Internet (well yes, there are terms that are not in our dictionaries, so we have to search for them in available texts about the topic we are translating).
What I would like to say with that: domains might not be relevant to somebody searching for just one word every now and then, but they are most relevant when you want to use a ressource in a professional way.
Thanks for considering to have Domains within OmegaWiki.