I host a couple of wiki based sites, so there is a lot of content at various stages of generation, and lots of links to pages that have yet to be created. Of course, these links are generating soft 404 "errors" when Googlebot crawls the site.
There was a good answer given in: How to fix soft 404 in an Ajax Driven website? The suggestion was to put a no-index command in the robots.txt for each of the not yet created pages.
However that sort of defeats the purpose of the flexibility inherent in the wiki format. The wiki shows the "missing" page links in red, so this is not a user experience problem, but rather, it is kind of the point of a wiki, to encourage further content growth.
So I guess the question is "does it matter?" How worried would you be about this if it was happening to you? I have never really had great rankings, and I'm wondering if this could be part of the problem?