Another day another vertical ad product. Burst Media’s new offering stands out however in the way it defines its vertical however. The Trendsetters Network promises to target the 15-to-34-year-olds as they visit their favorite niche music, fashion and celebrity sites. Burst says it has a reach of 100 Web sites and seven million uniques in this category. We’ll try not to quibble that there can only be so many “trendsetters” in a that demo. After all, who is left to follow?