Why freeze memoization?

I was wondering what was the reasoning behind freezing the Memoizable
return values?

Thanks

to protect you from stuff like

foo = bar.memoized_method
foo.gsub!(...)
#do something with foo

If you did this and foo wasn't frozen then you'd alter what
memoized_method returned for all future calls - probably not what was
intended

Fred

Makes sense. Thanks.