My perception of the dream world also leads me to beleive that we are connected, and that external influences are a common thing. I posted a little of what happened in my shared dream a while ago its somewhere on the forum its been a while so I dont remember where it is.

While I cannot say it is FACT I am pretty damned sure that sharing is possible along with Dream characters sometimes being external to our own minds.

You can see that there are different types of people in dreams, some are our own creations and they have a limited response ability and are often too busy doing their own thing to even pay attention to you, and then there are the ones that look at you and you can see in their eyes that there is a whole person. One with emotions feeling and intelligence. They are other dream walkers perhaps, or spirits that have manifested within our dreams, if all the hype about poltergistes and hauntings in the physical world have any bearing think of how a spirit could show itself within the nonphysical of the dream world.

The idea of connectivity is an interesting one, on the physical level, yes we are connected at a quantum level, when you get down to the quantum foam of existance its all the same. Scince is currently researching.. well in some cases even at the application stage of harnessing that force that connects us, its called quantum fluctuation for those half life fans Zero point energy, th gravity gun is way off but we are starting to mess with the ideas so its not impossible
Anyway back to DC's

Before you go and rattle the people you meet in your dreams brains try and determine what they are. When you find the ones I am talking about you will know.

For me, its all in the eyes.

The reason you dont always find other DreamWalkers is becuase think about the area of the dream world... It actually dosent take up any space in the physical world now does it? So to me that would also be like saying that the dream world has an infinite area. So actually coming across another sentient being is tricky at best, we probably meet many dreamers but just dont know it as we will never meet them in the physical world. I have a feeling that when we enter the dream world we create the world around us. If thats so if another DreamWalker creates something similar to your perception the worlds overlap.
There is also the thought of certain places in the dream world being static. There are stories of Cities where dreamers congregate whether or not they exist I dont know but I will keep looking around.

Just keep exploring, and perhaps we will find one another.