A growing number of businesses use Twitter for advertising. This recent Wall Street Journal article elaborates.
It is very easy to sign up for a Twitter account, and it costs nothing. Each post has a maximum of 140 characters, so the message is very brief. To find a person or brand name to follow, simply search for the name and then click the "follow" button.
I use Twitter to follow the SharePoint brand name. I receive information on events, product changes, and trends. I have found the content in Twitter to be useful in some cases; for example, a link to an interesting article or news about a upcoming event. But the majority of the information I receive is useless.
And therein lies the secret for using Twitter. Always strive to submit content that is meaningful and useful for readers. Who wants to read this real excerpt: "Friday – what do I want to focus on today?"
...Bob Spurzem