I think a Makers mark is essential. I keep a log book for my knife purchases to record details like cost, materials, construction techniques, etc. I want to know a lot more than just the steel type.
Having a maker's mark is important to me, marking the steel type is not. That's only one small detail in the things I want to know about the knives I buy. I would not mind if a maker chose to mark the steel (some do), but I would not hesitate to buy a knife made by a well known maker on the secondary market which did not have the steel type marked. Usually it is easy to guess, or the maker can tell you the steel used.
There are many problems with this idea. How do you mark a pattern welded blade? What value would a marking like 1084 mean when comparing a blade by a master like Jerry Fisk with a 1084 blade made by a new and inexperienced smith? They would probably not be even remotely similar materials after the maker was finished. 1084 can be made into a lot of very distinct materials depending on heat-treatment techniques. It is the same with most blade materials.
I agree that it would be great to have the newer materials like 420V and talonite marked in some way. I would add a lot of value to a knife made with 420V compared to ATS34. So for knives on the secondary market, steel markings could both add or detract from the percieved value of the knife.
Nevertheless, I value the makers know-how, skill, craftsmanship, and artistic ability far more than the materials he chooses to work.
Paracelsus