LinkedIn is rather more important. It's still the largest professional database we have and a kind of rolodex.
Having worked for and still working part-time for a major, as in top 5, vc firm, investors will definitely look for you on LinkedIn early on to ensure that you're a legit person with a good job history and a network.
This is even more important, when they are hiring for themselves.
There are so many grifters in tech, that investors and people hiring for leadership positions in startups feel the need to be able to draw a connection between your network and theirs.
Moreover, if investors are interested in your venture, they'll want you to create a profile and assembles a network. It's part of having visibility for your venture and a certain amount of legitimacy in the community. A company is people, and their leaders need an online presence outside of Github and fora.
I'm sure people will jump in with all kinds of anecdotal counter-examples, but this is what I've seen in a few years working for Sand Hill.
I honestly would decline funding from investors that expected me to waste time on LinkedIn. Unless you are selling to HR, it's a pointless circle jerk.
From my personal interactions, and with my personal perspective of how Facebook has publicly conducted itself over the years, having worked at Facebook would immediately raise red flags in my mind about the philosophical perspective of the potential employee for having worked 'at will' at the company. Context certainly matters, but it would be become a point of conversation. Not all that different from a health-professional being wary of hiring someone who used to work for a tobacco company.
To me it would indicate the possibility that the person might not want to understand the wider implications of their work, might understand those implications but not care about them so long as they are personally or socially enriched, or might just agree with the duplicitous nature of the company. There are of course circumstances to account for, and everyone's reasons are different - but the above rationalizations would raise red flags for me - especially in my industry where thinking about wider implications of our work is absolutely critical.
I am not the GP but I totally agree and the same goes for NSA employees. They have proven they are okay with violating the privacy rights of a billion people.
LinkedIn is great for their intended use case of documenting and presenting your professional relationships for potential job offers. But LinkedIn doesn't connect you with potential customers.
Similarly, I'll be far less likely to hire one who has Facebook on their resume.