And when I say that, I am talking about the HN crowd. It's one thing to say "I can't believe people use IE6", but this is tech-savvy people using a joke of a social media.
Guys, if you want to look professional, buy your own domain name. Something professional, like yourname.me, or clever like "yourna.me". Build your own web page with your own damn profile and don't leave control over a company on how you look on the web. Be in control of the first point of entry to your identity.
For god sake guys. LinkedIn has had so many security issues, so much scummy behaviour regarding spam, user retention etc... yet you are still blessing them with your presence. (Obviously this doesn't apply to those that don't)
PS: Use gandi.net as a registrar for your name. They offer a free ssl cert along with the domain (and support almost every tld) for added "professional-looking" value to your site. I am not affiliated with them, I just love Gandi.
Edit: I'm being called out for "living in my own bubble" it seems. Yet LinkedIn is the very definition of a bubble. I used to have a LinkedIn profile and from it all I got were the most awful recruiting experiences, and all of them through cold calls. Your own site with CV + portfolio + Github + contact details is a LOT better.
PS2: Downvote or not I don't care, but please reply if you disagree; I'd love to disagree even harder!
Edit 2: I'm starting to think there is correlation between finding LinkedIn useful and not having a Github profile. A lot of the points people are bringing up here are solved in a very similar way by Github (which is in many ways a social network). This does bring me back to my original point though, why use LinkedIn when you can use a company that isn't scummy and actually have your real work experience on there and a link back to your personal website with more portfolio etc?