The simple answer to this question is that it's essential to your business. Good Internet branding is every bit as important to a business as normal, "real world" branding. In respect to your business, the Internet is every bit as real as the "real world."
Think of it this way. If you have all of your corporate branding in place before you set up your Internet presence, it should all be coherent, right? Your Internet branding should match your corporate branding; otherwise, people may get confused. They may think that your Internet presence is just some hacker trying to make money off of your name. The result is that your Internet business doesn't give you the results you hoped.
Not having your name, logo and other images of your business and products carry over to the Internet branding can also damage your reputation. If your logo is used, but the font of your company's name is wrong, or if any one of the myriad other mistakes that could be made are visible, people may think that you don't know what you're doing.
The first step in the process of Internet branding is the selection of a domain name. It'should, of course, match your company's name or the particular product you're promoting as much as possible. This is highly important, because that is the first thing the search engines look for.
Secondly, your corporate name, logos and motto should carry over into the Internet branding and be prominently displayed. There should be no question of whose page a user is at. If the product that you're promoting has a different branding than your umbrella company's branding, you should use that in preference to the whole corporation's branding. Mountain Dew is owned by PepsiCo, but the Mountain Dew page is covered with that imagery, not Pepsi's. The same is true for Sprite and Coca-cola, or any other example you can think of.
If your company is the only one that has your name and imagery, you're pretty much guaranteed exposure on Google's first page. In the interest of Internet branding, you should have several pages. By utlizing this method, you can theoretically take up the entirety of the search engine's first page. This is the most effective way to protect your Internet branding. It keeps libelous and otherwise negative reviews off of the first page where others are likely to see them.
If your name is unique or if it isn't, your presence can be enhanced by Web 2.0 marketing techniques. It may be that the mudslinging about your company is on a page that would normally outrank yours. By implementing the techniques of Web 2.0, you can further protect your Internet branding by getting all of your pages ranked above these other pages.
All of this seems incredibly technical, and it rightly is. If you're a small business interested in starting up on the Internet or if you're a CEO of a large corporation, it's in your best interest to hire a highly skilled SEO firm to protect your Internet branding. The competition is using professionals for this; shouldn't you?