The issue I have with conjurers tricks, is that they rely on you to use your sense in the physical world to verify that which is beyond your physical senses.  Terms such as ectoplasm, raps and foot steps were invented during a prolific era of seances, and multiple ingenious ways of faking it have been documented.  Professional magicians can absolutely convince you that they are doing one and the same, and invite their methods to be tested. 

You are using the medium (conjurer) to explore for you - which is really not direct knowledge or knowing.  It is, by nature indirect.  The idea that a physical manifestation is more convincing is merely a manifestation of a belief system in which we validate physical reality as the "real" reality, eventhough it is a subset of what TC calls NPMR  - non physical reality.  LIke in a Venn diagram. 

I for one would be amused my ghostly footsteps, or a levitation, and I would be interested in figuring out the trick.  If my deceased mother was going to communicate with me, I guarantee that it would not be with levitating a table. 

There were several gurus who used to materialize black ash in India out of thin air and trinkets as a sign of their divinity.  Sai Baba was a guru who would go out into the masses and as a sign he was divine, he would make it seem that he materialized ash, watches, etc. to the public.  He was revered and almost worhipped.  In this video, some of the tricks/scams were shown on camera:

http://www.youtube.com/watch?v=EwOecpMkHH0

Yet the public swore it was real.  I am impressed if the tests are being conducted with scientific rigor.  Yet people may be misled, and I think the focus on the physical may be the wrong thing.  How do we break through our limiting belief systems; by reinforcing them with proof of the primacy of the physical world, or shattering them with being open minded about the non-physical world?