Paul Rand was famous for saying that a brand itself has no value. It only has value in its connection to the company and the behavior of the company. Thus, the IBM logo appears technological not because of the logo, but because it became associated with IBM.
I think that that is partially correct. It was certainly more correct in the past, but as the market has evolved, some of that truth has faded. As the market has become more crowded, the number of logos and brand constructions to which people are exposed has increased exponentially. This means that any brand that is created is already being interpreted through the lens of other brands.
As such, how a brand works and looks in comparison helps to determine initial interpretations. This is, of course, not a rule to be followed or a restriction of some sort. Instead, it is simply a state of the world that can be exploited as is, or specifically resisted to better stand out from the crowd. But still, it means that a logo and brand will have meaning and significance attached to it from the very beginning. It's why some logos look "professional" while others look "amateurish."
How is that determination made? By appeal to other brands.
I don't think that this is specifically positive or negative. In one sense, it means that a company has certain rules that need to be followed to allow for quick acceptance of a brand by the public. But it also means that a company can use these extant public perceptions to build an impression of being "corporate," "professional," and "big" without actually being that way. Basically, because of the huge history of brands, a company can fake being big.
This reality also makes skill in brand and logo design all the more important. A brand must follow conventions only insofar as it aids acceptance by consumers. The brand must then attempt to do everything else as differently as possible or risk being lost in the din of marketing. I think that this is why brand designs are so frequently as bland as oatmeal. Most designers do not have the skills necessary -- not for any fundamental reason, but just because they do not foster them -- and marketers believe that it is better to have a boring brand that follows all of the "rules," than a brand that strives to be something great but fails.
Rand's wisdom still holds up well after the brand has been introduced. Even though significant customer interpretation of your brand will happen before any interaction actually takes place, these interpretations can be easily changed by the actions of the company. What a company needs to be keenly aware of, though, is that the market has become such a loud goulash of other brands, that their presence has a large effect on any branding effort.