Would namespaces make reuse easier by permitting the "reusable" code to access private versions of otherwise well-known objects?  It certainly isn't the only problem, but a big enough one.  It may be valuable to approach code reuse the way one approaches porting.  Porting to a foreign environment is a pretty well understood activity with lots of grist for the pattern mill, unlike reuse which is more of a holy grail as you eloquently point out.

Ed