The wiki trap (that we've fallen into)
A number of years ago we had a not very good support website area that was basically a bunch of HTML pages with very little organization and navigation. In late 2009, when things reached the point where the support site absolutely had to be improved somehow, we made what has turned out to be a bad mistake: we turned it into a wiki. I say that this was a bad mistake because about a year later, we discovered that our wiki software was effectively abandoned. Oh, there's still something by the same name being developed, but it uses a different wikitext format and there's no automatic migration from the old wikitext to the new one. As far as we're concerned, it's different software.
This has left us seriously stuck. It's clear that we have to migrate but it's equally clear that doing so will be a significant amount of work because all of the content is 'locked up' inside the wiki's custom markup (and its file organization). Any means of getting an HTML version of the content will require stripping out what is probably a lot of standard markup and styling that the wiki adds, and we may have to resort to spidering our own site just to get all pages.
(We aren't even thinking about trying to extract the historical record of content modifications. That too is locked up inside the wiki, somehow, but it's not important enough to justify the effort to get it out. So we're going to lose stuff in this migration and no, that does not make me happy.)
In the mean time the wiki software has flaws like bad searching, the content has various issues, and the overall navigation needs to be improved, but doing anything in the current wiki is pretty much a dead end. So we mostly haven't touched it; we make minimal changes to update the content when we change our systems and every so often some especially dedicated person does a little bit more. Deeper issues of structure and wiki features remain completely untouched, partly because modifying the software ourselves is just not going to happen.
(Maybe we could do some of these changes without too much work. But every time we contemplate spending some time learning how to improve the current wiki, the inevitable question is why we don't use that time to start figuring out how to migrate and what to migrate to instead of wasting it on work we'll throw away.)
This is what I'll call the wiki trap: once you put your content into a wiki you're probably stuck with the wiki, for better or worse, because migrating away from a wiki you've adopted is generally quite difficult. A wiki is a one-way ratchet, a place where content checks in but it never checks out.
(Technically you can have a wiki that stores content in HTML form. This wiki would not have this issue, assuming that you can get at the raw content. The other way out is for your wiki to support exporting content to raw HTML. By the way, I'm still ignoring the edit history here.)
I don't have an answer to this situation. In fact this situation makes me very unhappy. I like wikis as a general rule, they give you a bunch of convenient features in one place, I really like simple markup, and there's a lot of appeal to allowing a broad bunch of people edit access to our support documentation so they can improve it. But at the same time I can't deny that putting our content into a wiki has turned out to be very painful experience in a way that could easily happen again with pretty much any other wiki software that we move to. It really looks like we'd be significantly better off with our content in dumb HTML in the filesystem (and assembled into web pages in any number of brute force ways).
(You may be tempted to say that our situation is an exceptional one caused by an unwise choice of wiki software. At one level this is true, but at another level how long is the life of the information that you're putting into your wiki now, and how sure are you that something this could never happen to your wiki software over that lifetime? I'm not sure that I can bet on any wiki software that I want to use to have a fifteen year lifespan, for example, and some of our support documentation is likely to live that long.)