Really what’s changed, the big things that have changed, added to the header of pages, I would tell you generally speaking that you should think and worry about:
- Twitter Cards
- Open Graph markup
- The favicon
Twitter Cards is pretty obvious. Basically, because Twitter is such a big distribution network for content and can be, it pays to have your cards optimized rather than to just have the URL exist on its own. You can stand out better in Twitter that way.
Open Graph markup, this is basically used by Facebook, an even bigger distribution platform than Twitter, and so of course you want to be able to optimize how you appear in those. Because social media in general is so well correlated with all sorts of positive SEO things, you want to put your best foot forward there. Therefore, I’m going to say this is an SEO best practice as well as a social media marketing one.
Favicon is a little weirder. Favicon’s been around for forever. It’s the little graphic that appears in your browser window or at the top of the browser tab. The reason that it matters is because so many sites — social media platforms and many distribution sites, places like Pocket, places that scrape, places that will show your stuff including sometimes, at least in the past, Google’s knowledge cards — will sometimes use that favicon in their display of your site. For that reason, it certainly can pay to have a good favicon that stands out, that’s obvious and clear, much more so than it was, say, a decade ago.