For me, I use LinkedIn as my work memory. I've been working since 1987 and have had gigs at so many companies, and worked with so many good people over that time that it's literally impossible for me to remember my own resume (let alone names and faces). It's how I stay in touch with the people who move around and may be the one to help me get my next gig.
A lot of people on HN often go on about freedom of speech, but it just seems to me that where people are happy to defend asshole's speech, no matter how terrible, the kind of saccharine, do-gooder, positivity found on LinkedIn gets torn to shreds. Live and let live. If it's not your cup of tea, please feel free to develop and use an alternative. I'd love to see it. Unless its full of people being total assholes. Then I'll stick with LinkedIn. And HN.