if you were to believe this possible(which i also do) u would need to agree that telepathy is to some degree real also....that being said...is there a limited DISTANCE to which ones mind could reach another? i believe its possible for 2 ppl in the same room to share a dream but VERY VERY HIGHLY unlikely that u can share one with someone half way around the world, or even a few hundred miles away...if you could the dream world may very possibly be as crowded with real ppl as the real world...
then there is the chain idea...but that would require alot of people...making "pitstops" or "dream boosters" with other people like a chain....dividing the distance into smaller segments...but thats just my thought for the day on this =) maybe i'll elaborate more later if anyone responds lol.