<rant>
There's been much talk about content, and sources, and whatnot. I think alot of this debate has been caused by confusion over some of WP's fundamental policies, particularly WP:NPOV, WP:V and WP:NOR.
Firstly, I'd like to point out that WP:NPOV has *always* had a threshold to it. People are getting all worked up about a content cabal over nothing. Exclusion of minority opinions has always been policy. Not every theory can get in just because someone published a paper on it. Scroll down to the second heading and read the quote from Jimbo:
"If a viewpoint is in the majority, then it should be easy to substantiate it with reference to commonly accepted reference texts; If a viewpoint is held by a significant minority, then it should be easy to name prominent adherents; If a viewpoint is held by an extremely small (or vastly limited) minority, it doesn't belong in Wikipedia (except perhaps in some ancillary article) regardless of whether it's true or not; and regardless of whether you can prove it or not."
If, out of a collection of say 100 scholarly articles, less than 5 of them represented a particular POV, that POV does not deserve inclusion. Of course people will quibble over what "minority" means, but we can always have a vote on the talk page to see whether people consider a source to be a minority source.
Many of the examples discussed here are trivial and not the kind of disputes which actually happen. Re trains: it's ok to cite some not particularly well known train-related archive, as long as train buffs know about it. WP:V says:
"In general, consider the sorts of people who are likely to edit the article in question: the article should be verifiable by these people. Therefore, an article on a sociology topic might include content that can only be verified by a sociologist."
The problem articles are generally not the ones with little information available about them. Generally, they aren't contentious, and if they are, they probably fall under WP:V or WP:NOR, in which case they can be dealt with quite easily.
No, the problem articles are the ones where one large body of people coming from one POV are confronting another large body coming from another POV. But of course it is not WP's role to solve these disputes, merely discuss them. Some people seem to forget this. If the process of WP:NPOV (weed out the minority sources) cannot arrive at a consensus set of facts, then that's fine. If we can't, then the real world probably can't either. We just present the opinions and move on.
All that is necessary for POV to prevail is for good Wikipedians not to read/enforce WP:NPOV properly.
Now it's late and I'm going to bed. Apologies for taking up so much inbox space.
</rant>