Any pitfalls to the nil index idiom?

[Dirk Laurie <dirk.laurie@...>]

It has several times been noted on this list that you can have e.g.
tbl.a.b.c.d.e evaluating to nil if any intermediate table does not exist,
instead of raising an error, by

   debug.setmetatable(nil,{__index = load''})

Is there any subtle undesirable consequence to doing this?