I have heard stories with ppls success on housing beardies together, in appropriate space of course and then,
I have heard stories with ppl who were unsuccessful, usually in results of MBD, severed limbs, and parasitical stress.
It is really the individual bearded dragon that decides this.
However, I will offer my opinion based on bearded dragon habitat and behavior.
In the wild, bearded dragons rarely come into contact with eachother and when they do, it is usually over breeding or territorial defense/offense.
If you house two males together, they may end up fighting, sooner or later...
If you house a male and a female together, they male may mate with the female prematurely and/or agressively during the breeding season, and throughout their lifespan, either sustain physical and emotional injury and stress.
I think that if you are considering housing two dragons together, it be in an extremely large tank (no less than a 210 gallon) and that it be two females, bought in same proximity of age and size.