Brands should be using Flickr to interact with their audience in a highly visible way. Take a look at PSFK's Cool Hunt competition and the themes we've chosen (cool jeans, cool robot, cool bike). Could you do something similar?
There's also another possible danger: think URL squatting. Right now anyone can open and secure a group name that is the name of a brand. What happens then? Hopefully it's some nice fan. Maybe it's not. Here are some examples we made earlier: