Lawyers need to use LinkedIn to have it pay off for them. The ABA Journal notes that Social Network Sites Only Work for Lawyers Who Work at Them, and in addition to building connections or building recommendations, one way to work at LinkedIn is to participate in the Question and Answer sections. LinkedIn may not change your practice much if you merely set up a profile with a few connections with other folks around the office.
Steven Shimek talks about how interacting via the Questions and Answers feature on LinkedIn has helped him bring over $250,000 of new business to his public relations firm.
There are plenty of LinkedIn members seeking legal counsel as well, as you may find almost everyday in the Law and Legal Question and Answer section, and those that I work to post on Twitter. You can see some examples of these type of client inquiries in My Tweet Sixteen - http://twurl.nl/kmrdu4
"Facebook for Lawyers" is a 65 minute recording (audio and computer screen capture) of an online seminar conducted by David Barrett on how Facebook can be used as a business development tool for lawyers.