An attorney at my firm recently asked me, in effect, if I thought LinkedIn was sufficiently professional that it would not embarrass her if she joined.
I answered that, yes, it was pretty far along, and that I thought there were several hundred thousand lawyers on that service.
(I have also suggested to a KM colleague looking for work that before she did any more research or on-line work she should get herself a Linked-In profile, as the absence of one might hurt her.)
I knew that my firm had its own company profile (which has 930 current employee members, plus former employees and other hangers-on) I wanted to check my math and found this useful and graphical post from Steve Matthews at Stem Legal Web Enterprises, suggesting that there were 840,000 people in the "legal practice" category in LinkedIn as of June 2009, up from some 406,000 in December 2008.
LinkedIn is not limited to the U.S. by any means, so I ran my own search and identified 627,302 U.S. people in the "legal practice" and "legal service" industries.
Let's assume that half of these people are IT, administrative, or marketing staff (a conservative assumption, for instance, at my firm more than half of the people are lawyers). So that leaves something north of 300,000 lawyers on LinkedIn (yes I pat myself on the back).
To put that large number in context, the ABA reports (based on reports from state bar associations) that were are a total of 1,180,386 lawyers in the U.S. at the end of 2008. So we are at around 30% adoption--well past the "early adopters" and into the "early majority," the middle of the adoption curve on LinkedIn. And the rate of growth--doubling every six months, four times that of Moore's Law--cannot be sustained, because we will run out of lawyers in about a year!
I have found that LinkedIn has greatly improved lately through introducing status updates, useful groups of various kinds, and good guesses at who else I might want to be connected to. These Web 2.0 features and its ubiquity help explain its success.