A company is only as strong as its branding. When you think of the most powerful, influential companies, it is hard not to think of their branding; if I were to mention a Bull logo, odds are good you would think of Meryl Lynch, for example. The same applies to most companies that have climbed to the top of their corporate hill and planted their flag there.
This is not to say that the logo design has to be particularly strong, only that a company that has not looked at its corporate identity design and debated what that design says about the company, is probably not doing as well as it thinks it is.
The reason for this is pretty basic: We, as humans, tend to think in terms of the visual, and look for symbols to fall in behind. Plain text just does not get our fancy as much as a lion, a mountain, or even a simple blade of grass. It can be argued that part of the success of today’s religion is based on their use of symbols; Judaism’s Star of David makes for a simple way to determine who follows the same god. For a great example of an ancient group with an easily identifiable corporate ID look at the Roman Empire; if you saw one of their flags flying above even a small settlement you were unlikely to mess with it.
Logo design takes a very close look at how the company wants others to look at it Federal Express changed its logo in order to better highlight that they go anywhere; even in plain text, the white space between letters E and X makes an arrow if you look at closely, and that is just what they wanted to better emphasize that they go. Lucent wanted to tie into innovation, and decided that coffee was the sign of innovation at the time; it was the company that started the “coffee cup stain” logo design concept; suffice to say that they changed it once it was no longer innovative.
The modern heraldry is corporate identity design. The branding has to be unique, and has to combine old symbols with new ways of looking at those symbols. The corporate ID has to be unique enough that it can be quickly identified, but has to draw meaning, meaning that states why that company is important, from symbols that mean something to those that see it. By combining these, a successful corporate ID is made, and helps to make that brand look strong in a field of competitors.