I am not much of a social media person, so I don't usually sign up for new social sites, even when work related. Recently, I set up a ResearchGate site for myself, mostly as an experiment. A colleague of mine swears by it, and claims that his citations have really increased since he started using the site. It is an easy experiment to try, so I just set up my page, and let it go. So far, nothing I have seen convinces me that more people are reading my publications, but it is early days yet. Also, I am not illegally uploading my publications, so there is that. If I am still blogging here, I'll revisit my ResearchGate experience in a year or so.
My field is not really one that uses preprint servers much, though I have no real objection to doing so. I much prefer to read the nicely formatted journal versions (when available), rather than the preprints on the arXiv myself. I think preprints are a good idea, but peer-reviewed journals serve a beneficial purpose both in acting as gate keepers for junk (and I think anyone who has done a review knows that), and also in improving manuscripts. All of my own publications were improved during the peer-review process.
I have a few open access publications, and they are not cited at a higher rate than my other publications. All the data I have access to seems to confirm my own experience that it is not hard to get access to a paper, even if ProdigalU's library doesn't have it. Legally even. Interlibrary loan works, but it it slow. Faster is to just email the corresponding author. In my experience, they are happy to send a pdf (which is usually fine under the licensing terms--I have never even come close to sending out as many as I am entitled to as an author). Not instant gratification, but still pretty easy access to the literature. And that is before the quasi-legal or downright copyright violating methods. The actual fastest method is to just google the title, and often a non-pay walled link will show up. I just don't see access to publications as a major issue for most people with an Internet connection.
I get that some people have open access as a near and dear issue in their hearts. I get that extortionate journals are a problem, and that libraries are being squeezed by publishers to take on (and pay for) crap journals they don't want to get the ones they do through packaging. The thing is, open access doesn't solve this problem and adds new ones. Quite frankly, I can't pay page fees. I just don't have the money. Even if I did, there are not many non-predatory open access journals in my field, so I would just be paying more money to those same journals already extorting my library. Furthermore, at this stage in my career, the work that can go into high impact journals needs to go into high impact journals (mostly for the benefit to my CV), which means no open access.