A primary use has emerged for Twitter (NOT as a marketing or PR tool).

It's for keeping up on what's happening.

Marketing in general is a very fast moving field and Internet Marketing evolves so rapidly it is a real challenge to keep up. With a few Twitter follows, I'm sure nothing is passing me by.

Here are the key Twitter accounts for me (in no particular order):

1. @SEngineLand - SearchEngineLand is one of the two or three best and most reliable sources of information on the world of search.

2. @SEWatch - Search Engine Watch - Another top source for What's Happening with Google and the gang, plus (usually) reliable advice.

3. @Mashable - "Social Media News and Web Tips" - one of the giants of the Internet with a huge following.

4. @TechCrunch - A good source on Bleeding Edge start-ups, technology and data.

5. @PewInternet - Always insightful, sometimes stunning survey information on usage, habits, etc.

6. @Google - Official Google Twitter feed. Important announcements will appear here.

7. @MattCutts - Google's main spokesperson for Search.

Now that is only seven - and between them, they keep me at least 90% informed on what is happening in Search, Social Media, the world of Mobile, and other aspects of Internet Marketing.

Not bad.