I don't think sourcing is just an issue for new users. When I first joined WikiTree, I just put up the family members I knew about. I'm not sure that I had ever even heard the term "sources" in the context of genealogy. Then, I started reading a bunch of stuff about sources being important, and that dictum that says, "Genealogy without sources is mythology." To be honest, that really stuck in my craw. I know who my grandparents are, and ain't nobody can tell me different.
(Then, too, it brought up bad memories of math class in school, when I would get marked down, not because my answer was wrong, but because I didn't show my work. I'd just work it out in my head, but my teachers wanted me to write down every step of the process, which would take way longer than finding the answer, so that annoyed me, too.)
But eventually, I calmed down somewhat, and realised that, while people might overstate the case, they do have a point. I know what's in my head, but nobody else does, and if we're going to be able to work together on building one world family tree (which is, after all, what we're trying to do), then I need to share, not just bare facts, but how I came to learn those facts. (Well, not just me, everybody.)
So then, I had to go back to all the profiles I had already created, and source them. (Okay, true confessions time: I still haven't finished that part.)
And then I read that sources need to be formatted in a particular style. There's a help page about that, but it only has eight examples: "Book", "Periodical", "Census", "Web page", "Family bible", "Cemetery headstone", "Second-hand information", and "First-hand information (yourself)".
(And, to be honest, I have problems with the examples given: not just that there aren't enough of them [because I have referenced all kinds of things that those examples don't cover], but also because several of them have problems even for the cases they do cover.)
Now, at the bottom of the page, it links to:
Elizabeth Shown Mills, Evidence Explained: Citing History Sources from Artifacts to Cyberspace, Baltimore, MD: Genealogical Publishing Co.; 3rd edition (May 22, 2015). See also the author's blog by the same name: Evidence Explained.
but to be honest, I haven't shelled out the money for the book, and, however great it may be, I'm not sure that all that many other people would, either. (Professional genealogists, sure. Even keener amateur genealogists. But for dilettantes like me, shelling out over $70 for a hardcover book is just a wee bit more commitment than many people are willing to make.)
So essentially, what I'd like to see is more (and better) material on that page. Although as the list grows to cover more sources, we'd probably have to spawn sub-pages for different cases.
I'm sure that most (if not all) projects have lists of resources, and that's good, but I'm pretty sure that we don't want to have sourcing style guides at the project level, or else we'd have one project telling people to do sources one way, and a different project telling people to do sources a different way. Since Evidence Explained is the "official" style for sourcing, then we should have some document applying to the whole site that explains how that style works in different cases.