I do not think Myspace could have saved themselves through brand advertising, because Facebook wasn't attacking them at a mass audience level; they cornered the college market, school-by-school, then methodically expanded social-group-by-social-group. According to the research, in most categories, recommendations from friends and family is far and away the most important influencer. Advertising doesn't come close. And anyway, this is very much the opposite of mass market awareness; they did exactly what a startup SHOULD do, which is narrowly define their audience of early adopters and then focus all their energy on a growing a critical mass of adoption there. Then, and only then, should you consider growing to a broader audience.

Also, good advertising can never save a bad product.