The last places I've bought tubes from were in boxes labeled 'Specialized' (LBS), REI, 'Forte' (Performance Bike), and from JensenUSA (online). When opened, the tubes were all labeled with Chinese manufacturer's logos (Chen-Sing or other). I'm wondering if there's really any difference in the generic Chinese tubes and those made in China for brand-name companies, because I haven't been able to distinguish any differences between them. I'm using both 700 x 32c (or 28c) and 26 x2.0 (or 1.5) tubes and tires.
FWIW: I stopped getting regular flats when I started using puncture resistant tires, so I can't blame the tubes for the few flats I do get each year.