Daniel Pink author of the classic, "A Whole New Mind," (see required reading) was recently quoted as saying, "To be in business today, you have to be literate in design—and the impact of that design to differentiate." The rise of Web 2.0 and the active participation of consumers has made design a key way to differentiate yourself from the competition, both online and off.
Obviously, a product that is easy to use will attract buyers when compared with a difficult one. But, consumers have begun to DEMAND good design and reward those who make it a priority.
This has never been more true online. Blogs, newsletters, websites and business cards need to work together to brand and communicate your message. I think the days of getting by with a poorly designed online brand is over.