Originally Posted by séamuis 
most canon and nikon lenses and bodies are made in Japan, and guess what? all sorts of QC issues to be found.
Sigma too is assembled in Japan and has enough qc issues - however my dealings w/ their service center last year (about 17-70/2.8-4.5) showed at least one positive things - they will replace the lens itself fast and no questions asked for as many times as you want it...