Proposed resolution (September, 2010):

Change 9.6.2 [dcl.fct.def.default] paragraph 4 as follows:

...A special member function is user-provided if it is user-declared and not explicitly defaulted on its first declaration. A user-provided explicitly-defaulted function (i.e., explicitly defaulted after its first declaration) is defined at the point where it is explicitly defaulted; if such a function is implicitly defined as deleted, the program is ill-formed. [Note:...