In a new info graph by LinkedIn and Vincos, the legal profession was the second to the last industry utilizing LinkedIn.

This just in! LinkedIn announced earlier this week that they now have more than 100,000,000 users. Just to put that into a bit of perspective, if you were to stack 100 million business cards in a pile, it would reach 98,425 feet, according to Read Write Enterprise. You’d pass Mt. Everest at 29,029 feet. Let’s just say, it’s a whole lot of business professionals in one place.

But here’s what I found particularly interesting in regards to law firms. Attorneys are not anywhere near the top users of LinkedIn. In fact, much to my surprise, law firms are surpassed by construction, government and transportation, industries not generally considered particularly social. In fact, only agriculture falls below legal on the chart seen here.

On the flip side, industries like hi tech, manufacturing, finance, medical and corporate are on LinkedIn in droves. So if you or your law firm target any of these industries, you can bet that your clients, and some pretty excellent prospects, are probably on LinkedIn ready to be linked to you.

So what does this mean? First, I realize that law firms are not always on the cutting edge of new technology. But at 100,000,000 users, LinkedIn has been well-vetted and is now completely mainstream. So if you aren’t on there, it’s time to get on.

Secondly, just joining LinkedIn is only the start. Fill out your page completely, including job history, specialties and education. Get recommendations and add PowerPoint presentations and PDFs by using Box.net. If you have a blog – and you should – add a blog roll to your page. And this is just scratching the surface. The expanded functionality really makes LinkedIn a very valuable resource, so take advantage of all it offers. Oh, and don’t forget to create and complete a page for your law firm as well!

If you want to see an optimized company page on LinkedIn, click here to view ours.

I’ve talked about LinkedIn regularly on The Matte Pad, so read here, here and here to get started and learn more.

Now for a few fun LinkedIn facts.

• In a 24-hour period, mobile usage is highest at 5 p.m. PST.
• The fastest growing countries are Brazil (by far), Mexico, India and France.
• 1.5 million new people join a LinkedIn group every week.
• 61% of LinkedIn users are men
• 36% of users are in the 25-34 age range, and another 36% are in the 35-54 age range.