They break up text copy and serve you as mini-headlines with an entirely different look and feel. The ideal length for a bulleted list is 3-5 items, which is probably the most readers scanning can grasp. If your bulleted list is too long, try combining several bullets into one. This will help you get better search engine rankings, and it makes your pages easier to scan. Be sure to use your keywords in this 'opening salvo'.
People can only read one screen of information at a time.
If you are looking at a screen shot of text on your Web page that is one continuous paragraph, it's way too long. Short paragraphs of 2-3 sentences apiece will serve you better, and each can have its own subheadline. Your site visitors want to understand, NOW, exactly what your product or service can do for them. Don't use long sentences when short ones will work, and don't use long words when short ones will do. Write for results, rather than to impress.