Don't. The target group of LinkedIn is mid-level managers of any kind plus the people who want to join that group. Individual contributors such as programmers

Don't. The target group of LinkedIn is mid-level managers of any kind plus the people who want to join that group. Individual contributors such as programmers will not get any value of such a network - no job to be done. GitHub is way better suited, but won't capture the purely professional programmer who never works on public stuff. Leaves StackOverflow, maybe expand the user profiles into a full profile (maybe already done, not using SO myself as I am said mid-level mgr). Basically - you need a hook. Something useful on top of the networking aspect to attract ICs. Career-focused people are on LI and use it, no matter what. Very hard to beat them by now, similar issue with FB - to compete you'd need at least equivalent data. And yes, LI built their dataset with very slimey tactics.