Having separate meaning, determined by context, means that you don't have to use as many distinct identifiers in your program. This is especially pronounced if you're trying to use short identifiers, because there are fewer short identifiers that have some intuitive meaning attached to them, and I think it's useful to allow context to alter this meaning.
However, now that I think of it a bit more, making Arc a Lisp-2 would interfere with using compound data in the place of functions. If you have a symbol whose value is a compound type, and that symbol also has a function value, that creates an ambiguous situation. I'll have to suspend my opinions about Lisp-n-ness until I've used Arc for a while.
I'm a big fan of using identifiers such as 'list, 'string, 'fn (isn't a problem in CL, but is one in Arc), 'array, 'char, etc. Often a general name is the most concise and appropriate name to use.
I think that since Arc is supposed to be designed towards flexibility and usability for the programmer, it should have few restrictions, and a common namespace is such a restriction.
However, my opinion on this could change as I explore Arc over the next few weeks.
