Most of the country uses the International Code Council codes (ICC) . Section R502.7.1 of the 2006 International Residential Code says:
Joists exceeding a nominal 2 inches by 12 inches (51 mm by 305 mm) shall be supported laterally by solid blocking, diagonal bridging (wood or metal), or a continuous 1-inch-by-3-inch (25.4 mm by 76 mm) strip nailed across the bottom of joists perpendicular to joists at
intervals not exceeding 8 feet (2438 mm).
The 2009 code is the same except for the following exceptions:
Trusses, structural composit lumber, structural glued laminate members and I-joists shall be supported laterally as required by the manufacturer's recommendation.
So basically, bridging is not required for dimensional lumber 2x12 or less. End bracing, i.e., rim/ band joist and floor sheathing is considered sufficient. That being said I still prefer to see it.