Are scratched glass bowls safe to use?
The reason not to use scratched glass bakeware is because the internal stresses encountered during heating can (rarely) cause the bakeware to violently fracture along the scratches. That doesn't really apply to glass tableware, which doesn't encounter the same temperatures (though cracked tableware, of multiple materials, will occasionally break from thermal stress in the dishwasher). 

Incidentally, glass bakeware and tableware should be made from borosilicate glass, which cannot be scratched by steel cutlery.

EDIT: Also: Don't use glass tableware for hot food. Irrespective of safety issues, the thermal density and thermal conductivity of glass means that it will quickly wick away heat from any food which is placed on it. Glass plates are fine for salads and stuff, but they don't make good general-use dinner plates.