The Avatara are the most powerful mages there are (ont he light side) and lets be hnest it is not a good Idea to have hundreds of REALY powerful mages walking around, by limiting the number of multi-dream mages, theirs less chance of them converting ot the "Dark Side". You'll spot it sooner in smaller numbers, but sometimes they'll slip through the fingers eg Deciever, Moytirra, Mjarin (who may have been under the control of the Leveler at the time). But they're the only Avatar we know of to convert. If their were more Avatar then it is logical then there would be LOTS of other conversions.
Secondly the Avatar aren't just powerful mages, their also important public figures, eg Generals, probably advisors ot the Crown, And the leaders of the University. EG, Terry Pratchetts Discworld's Unseen University.
Also back to the dark conversions, It isn't a good idea to give the magics to just about anyone, its more logical to only spread the knowledge of FULL dreams to those who you can trust and thus a very select group.
Its just practical. Obviously their be Archmages just below the level of Avatar who would know one or two dreams, or parts of Dreams.
There, I think thats a fairly decent argument wothout going over old ground or going into a "yes there are""no there not" argument.
-zeph
