I read this Wall Street Journal article per the recommendation of @actonmba. The author chronicles the strategies small businesses use in social networking: from paying consultants to do it for you--to getting training--to doing it on your own. As a consultant working on these projects, I like the article's conclusion: use social networking in a way that works for your needs.
Doing Twitter Yourself
Over the summer, I worked with Isaiah McPeak, to begin using Twtter to connect with his customers. As I explain in my portfolio page, his primary customers are teens and their parents--he needed a way to connect with them beyond maintaining a blog. I proposed he begin using Twitter and it be a centerpiece of his new website. Now he connects directly with 50 followers and every site visitor (400-500 per month) can see his latest tweet.
Maintaining Twitter himself enables Isaiah to build a direct connection with his customers and stimulate a conversation about educational debate. It wouldn't make sense for me to maintain his Twitter--the idea is a direct connection from his expertise to his customers.
Ghost Writing Blogs
This fall, I've been working with Yellis & Foley CPA on their marketing efforts. In addition to building their first website, their LinkedIn presence, and their local search listings, I've implemented a 'Tax News Blog.'
The partners at Yellis & Foley use the blog to disseminate updates on tax news and online planning tools. However, because they are simply publishing information, they don't need to actually post each entry and manage the feed themselves. Contracting this service out to me increases the effectiveness of their campaign. I can optimize each entry for search engine placement and publish the feed in appropriate channels--things they'd have to invest significant time to learn before doing.
Conclusion
I think there is a general rule here. When businesses want to use social networks in to further an essential conversation, they should own the effort themselves (with appropriate training and support). When businesses use social networking as part of their marketing scheme, they can outsource its implementation.