... and why should I?
The answer to the first question is ... http://ping.fm. Ping.fm actually lets you update a whole bunch of social networking, blogging and messaging applications with a single message.
Event better, I can use twhirl, an AIR based twitter client, to update Ping.fm so I don't even need to go to the website, I can do it straight from my desktop.
So why should I?
Well, I have two twitter accounts. One is for business and technical use and the other is for my personal use. My tweets appear on my company profile on my company's website:
And because of Ping.fm those tweets are also appearing on the LinkedIn.com:
What this is doing is keeping my contacts up to date with what I am up to, but more importantly it is keeping me in my contacts' peripheral vision in the hope that I can provide them with some service further down the line and they'll think of me first for related activities.