That is a hard one. I think it depends on the market, really. In college, two of my gaming group were White Wolf writers. They weren't really known outside of a few credits, but they just fell into popularity and one of them has a dozen books on his credits and is the "special guest" at most of the conventions he goes. He just fell into it without a brand.

On the other hand, I have split efforts. For my other pen name, it was kind of falling into it, most of my sales were word-of-mouth and I have a small following but it is also very for a very niche market. My novel hasn't sold that much on that side, mainly because of a couple factors, mainly a publisher who closed their doors and didn't send books out, but also because it was hard to break out of that specific niche. But, if there is a brand, its fairly well established but I did no effort to really earn it. If I did, it was just moving from forum to forum, writing things that were interesting that got people reading more of my stuff.

For my mainstream pen name, I definitely feel the need for brand. Mainly because I'm a nobody in the market. Most of the rejections were based on my lack of impact on anyone's radar. I'm a nobody, and I think that has an impact on things. So, at some point, I'll probably have to make up a Brand new me :) and figure a way out of it, but I suspect it will be a lot of hard work when it does happen.