Occam's Razor. A business dominating a given industry is unlikely to engage in an advertising campaign (however guerrilla/viral) which (A) demeans its brand by

Occam's Razor. A business dominating a given industry is unlikely to engage in an advertising campaign (however guerrilla/viral) which (A) demeans its brand by referring to itself as "Dumb" and acting in a downright bizarre manner, and (B) there is nigh unto zero potential market share which would both be affected/informed by such a stunt and unaware of the business in question. The parody might benefit Starbucks, but nonetheless Starbucks will now have to combat the "Dumb" prefix and weird storyline. Were this to happen on/around April 1, I'd give you benefit of the doubt (Starbucks does promote some funny/odd notions on April Fool's Day, but even those have a strong sense of "hey, that's a darned good idea anyway").