Check out the latest issue of EC&M, page 84.
The 2005 NEC contains a slight change to permit "identified" handle ties, rather than "approved" handle ties.
Art. 100 defines "identified" as "recognizable as suitable for the specific purpose ...".
Art. 100 defines "approved" as "acceptable to the authority having jurisdiction".
A nail as a handle tie had been "approved" in the described and illustrated case.
So, if your authority approves a nail as a handle tie, then you're OK.
However, after the 2005 NEC becomes effective, only a manufacturer's handle ties will be permitted.