You??e heard of ??icrocelebrities?on the web. Now they’re endorsing equally small-time businesses online. I logged into my gmail account this morning to read an invitation to a friend’s party in Brooklyn. Sitting above it I see this sponsored link: “The Kid from Brooklyn shares his secret for romancing broads.” Sure enough, it’s YouTube celebrity “The Kid From Brooklyn,” best known for his vulgar rants against Starbucks and Yankee Stadium. Now he’s shilling for www.48longstems.com, a site that sells “roses the size of my freakin’ fist!” according to the Kid.