This applies both to actual celebrities, and people who are building a brand that can be clearly defined as having a "voice." People like Perez Hilton, Oprah Winfrey and Tony Hsieh of Zappos immediately come to mind. All of them have Twitter feeds and each of them has a very distinct voice. A recent post from the CEO of a company with projected 2008 revenues of $1 billion: "In waiting room at doctor's office. In addition to magazines, they should offer a selection of paint so people can watch it dry." People follow these feeds for a variety of reasons but mainly because they receive something emotionally satisfying from the postings.
The Guide is typically a person or people assigned to seek out messages posted by people with questions related to a certain topic, products or services they have expertise in. For example, this Blackberry-related company set itself up as a Blackberry trouble-shooter.
Someone proactively seeking out mentions of their company name or product name and responding personally to each post. Companies can win big brownie points by having very senior staff members respond to customer service questions. The idea here is that by providing direct access to someone who really knows what they're talking about, companies can prevent damage to their brand from disappointed customers.
Very similar to the Brand Watchdog, this too is focused on watching for and responding to customer service questions. This category is usually filled by the unsung Twitter heroes (Twiroes?). They are likely handling questions in other (non-Twitter) venues and have added Twitter to the ways they communicate. The catch here is that some Twitter customer service reps will actually help you resolve your issue. We'll see how long that lasts!
People and companies will often use Twitter as a way to simply feed followers information about their area of influence. A lot of news is now breaking on Twitter before it hits major publications. But you don't have to be first, just relevant and somewhat consistent. A really interesting take on the publisher model is The Brooklyn Museum, which is monetizing their social content and their community by offering memberships to a "socially networked museum membership" for $20 per year.
Both spammers and e-commerce sites fit into this category, but the e-commerce sites use Twitter in interesting ways to do promotion and inform customers about products they are interested in. Take a look at Amazon on Twitter. Their feed is a little bit all over the place in terms of content, and they don't have an individual person that followers can connect with (which limits conversation and can limit follower numbers) but they've still managed to collect almost 4,000 followers as of the publishing of this article. Contests, Twitter-only discount codes, and free giveaways are all part of the promotion channel arsenal.
Many of the most popular tweeters are those who actively engage with their followers. In essence this is what really makes Twitter unique as a communication tool, although it's also what scares the bejeezus out of small business owners. Being the Conversationalist can be very time consuming, but the rewards are high in terms of building a loyal following and truly connecting with people who are interested in what you have to offer. This approach involves talking several posts per day, many of which are directed at specific people.
There are many people who don't post to Twitter at all. They use it as an information resource, watching the Twitter trending topics to crowd source their news or follow people they find interesting or informative. This can be a great way to use Twitter and learn a thing or two. The key here is to be careful about who you follow – you want people with a high signal to noise ratio, usually with infrequent, but high-quality posts. -- Maisha Walker