On the other hand, Amazon and Yahoo have developed brands that, for the most part, only exist online. Dotcoms need to carefully execute their brands and remember that there are more restrictions due to the constraints of the Web.
Your logo is a visual cornerstone of a company's brand. Your company's identity is visually expressed through its logo, which, along your company's name, is one of the main things that makes your business memorable. Think of eBay, Google, and Yahoo. Each one of these companies has a distinctive logo that a large percentage of people would be able to describe without seeing.
Your domain name is also an essential part of your branding efforts. Unfortunately, it's becoming increasingly difficult for companies to find available domain names. While a URL certainly has to be unique and easy to remember, it doesn't necessarily have to relate to what you sell in order to be successful. How does the name "Amazon" relate to books and other products? Or "Google" to a search engine? These are successful names and brands, but it's a stretch to say they have anything to do with the companies' offerings.
Even if your business is an Internet-only venture, that doesn't mean you can't brand offline. You can get offline brand exposure through TV, radio, print advertisements, and public relations efforts. Remember, a brand constantly reinforces a business's identity, even that of dotcoms. Most likely, you already strengthen your brand in ways you don't even think about: distributing business cards at trade shows; sending invoices, letters, and holiday cards to your clients; wearing your company's logo on a T-shirt; and a variety of other activities.