I've recently noticed people's Twitter accounts ranking particularly highly on search results for their name. So is the benefit to your search engine ranking good enough reason to get into Twitter, even just as a token gesture?
For example, I run an experimental Twitter account for Puffbox: it's just a Twitterfeed thing for blog posts specifically about the company. It only has a handful of subscribers, and I'm neither offended nor surprised. But it's ranking remarkably highly on Google searches for 'puffbox': at present, it's number #3, beneath two results for puffbox.com itself. Setting up a new Twitter account takes seconds; setting up a Twitterfeed something similar; and once it's up and running, that's job done.
Of course, a one-way Twitter account isn't going to win you many plaudits, or indeed many followers. But if it pushes your content up the appropriate search rankings, for zero cost and zero day-to-day (or even month-to-month) effort, surely it's worth doing? The choice of a sensible, search-term friendly username seems to be the most important factor; but don't forget to add meaningful 'personal' information to your profile, so people know where to go next.