So, LinkedIn is turning 10. The Next Web ran this comprehensive recap of the pivotal moments in its evolution — complete with jazzy infographic and a fun look back at its clunky 2003 web design.

LinkedIn’s main differentiator was being among the first user-generated content networks focused on expertise. As an early adopter (user 6818 — you can find your own member number embedded in your LinkedIn profile URL after “id=”), I pulled together some thoughts on what I’ve observed as milestones contributing to its success.

1. Recognizing that they are a data company, and making some high-profile data scientist hires like Daniel Tunkelang — and enabling them to attract strong teams.
2. Embracing mobile — a little late to the game, but a snazzy, much talked about tablet launch in 2012 and frequent updates since.
3. Continuously improving the social aspects for average users sharing content — image integration that’s easy on the eyes, a longer character count than Twitter, a Like feature just like that other social network.
4. Cracking the code for content original to LinkedIn. Other companies, like Facebook and Tumblr have shuttered similar efforts (here’s a good piece from RWW). While I’d argue that they have a natural advantage over Facebook and Tumblr in terms of shared audience purpose, they get credit for bringing in a range of thought leaders who make the site compelling and who become champions for the platform.
5. Moving from text heavy resumes only to portfolio display opportunities — presumably the success of Bēhance and others has prompted LinkedIn to cast a wider net by supporting more visual experiences.
6. Rolling out new applications like a new contact importing/ management service (see email offer at right — perhaps more compelling if the data pulls someone not in the office next to mine) that try to make LinkedIn the default drive for your connections.

While not a specific feature, I’d argue that LinkedIn’s ultimate killer app was shifting the social norm around job hunting. Back in the day, leaving a copy of your resume on the printer meant only one thing — you weren’t intending to stick around your current role very long. Now keeping your LinkedIn profile up-to-date is more a sign of career attention than looming transition. And arguably, in some fields today the bias is in precisely the opposite direction: people who don’t update their LinkedIn profiles are less likely to be actively engaged in their own career development — which as Tom Friedman reminded us last week in his bleak 401(K) world column, is a dangerous place to be.