Very cool, check out what LinkedIn sent me in honor of its 100 millionth member:

The text of that letter is:
“I want to personally thank you because you were one of LinkedIn’s first 100,000 members (member number 11147 in fact!*). In any technology adoption lifecycle, there are the innovators, those who help lead the way. That was you.
“We hit a big milestone at LinkedIn this week when our 100 millionth member joined the site.
“When we founded LinkedIn, our vision was to help the world’s professionals be more successful and productive. Today, with your help, LinkedIn is changing the lives of millions of members by helping them connect with others, find jobs, get insights, start a business, and much more.
“We are grateful for your support and look forward to helping you accomplish much more in the years to come. I hope that you are having a great year.”
Cool. Thanks, Reid!