It would suck/be expensive if the build messed up 1/2 - 3/4 the through.
http://www.3ders.org/articles/20140207-china-developing-world-largest-3d-printer--prints-6m-metal-parts-in-one-piece.html
Not terribly expensive, the metal can just be reused after all. Hopefully the expense of the occasional lost time/manhours and power to drive it is outweighed by the net gains over traditional manufacturing.
In the temperature and force range of molten metals there is not much that could clog your noozle or stall the filament drive.
sounds like additive “spot” welding printer 
… very interesting …