[plt-dev] parameterizations rationale

I noticed this comment in the '99 Revenge of the Son of Lisp Machine  
paper:

"An early version of MrEd supported bundles of parameter values as  
first-class objects, called parameterizations. ... This generalization  
turns out to be nearly useless in practice ... Worse,  
parameterizations defeat the essential purpose of parameters for  
separating global state from thread-specific state."

Of course, parameterizations are back. What was the change in thinking  
that led to bringing them back?

Thanks,
Dave