FORTUNE — It all started routinely enough. Noah Kravitz signed on with mobile device and app review site PhoneDog in 2006, and began using a company Twitter account to keep techno-gadget enthusiasts au courant with his often quirky views on new products and industry trends.  Nothing unusual there: Most companies — 76%, says a survey by New York City-based powerhouse law firm Proskauer — now employ at least one, and often several, social-media mavens to carry their marketing message into cyberspace. Moreover, when he joined PhoneDog, Kravitz was already a popular Silicon Valley technophile with plenty of influence. What could possibly go wrong? A whole lot, apparently.  In late 2010, Kravitz left PhoneDog — and, with just a slight change in his Twitter handle, took about 17,000 followers out the door with him. (He’s now editor-at-large at tech news-and-reviews site TechnoBuffalo.) So PhoneDog filed a lawsuit against Kravitz last July in federal court, alleging that those followers are, in effect, a customer list and PhoneDog’s property. The company wants Kravitz to cough up $340,000: $2.50 per follower per month for 18 months. A hearing in the case, PhoneDog LLC v. Kravitz, is scheduled for January 26 in San Francisco.  It gets weirder. Remember when parties to a lawsuit used to decline to comment until after a judge had spoken? Forget that. This brawl (which also encompasses Kravitz’s grievance over partnership money he says PhoneDog owes him, and a couple of other murky issues) has got both sides in the lawsuit — and many opinionated observers — fulminating online, from tech blogs to law firm web sites.  For good reason: PhoneDog v. Kravitz will likely establish some legal boundary lines, which are currently quite hazy, between employees’ personal use of social media and employers’ claim on those channels of communication. Courts have long held that client lists, built up over time on a company’s good name and using its resources, are company property. But do Twitter followers — or LinkedIn contacts, or Facebook friends — meet the same standard?  “There is a huge gray area here,” says Elise Bloom, co-chair of Proskauer’s employment law practice. She expects many more lawsuits like the Phonedog case before the dust finally settles.  “Because of the nature of social media, you have to share a certain amount of personal information and commentary in order to be effective,” Bloom says. “Attracting lots of followers and keeping them, which of course is what your employer wants, means that, yes, mixed in with the corporate messages, you are going to talk about planning your wedding or what restaurants you like.”  Fine, but it does raise the question: Is it your employer your followers are really interested in, or is it you?  Blurring the boundaries further, employees may assume that, if they use their own personal iPhones or BlackBerrys to tweet, connect, or friend, then whatever they’re doing or saying online is their own business — even if they use company-owned Twitter handles or other corporate-sponsored platforms to do it.  One way to avoid the kind of legal hugger-mugger PhoneDog is embroiled in: Write up a company policy on social media that everyone understands, which Proskauer’s survey says about half of all employers have yet to do (even though 43% report “employee misuse” of social media).  “The technology has moved so fast that policies have yet to catch up,” Bloom notes. Before unleashing employees in cyberspace under the company banner, she says, “sit down and think carefully about what you want to protect.” Then make sure employees get it.  At the same time, for anyone who wants to steer clear of Kravitz’s predicament, Bloom offers this advice: “The same way you have your own personal email and Facebook accounts, separate from your employer’s, develop your own Twitter following with your own personal handle. Create your own distinct, individual online persona.”  If and when you leave your current job, it just might keep you out of court.
The blogosphere is buzzing over a pending lawsuit that raises the question: At what point do your tweets become company property?