Steve Bennett wrote:
Anon make a lot of typo corrections, but are rarely bold enough to fix major problems in articles.
I've been noticing that this seems to vary based on subject matter. There are articles where no anon has ever made a useful contribution other than typo fixing, but there are also others where we get useful and well researched additions just popping out of the blue.
I believe what I'm seeing here is a variation in the pool of off-wiki subject enthusiasts who are aware of the article but don't otherwise contribute to Wikipedia. For some subjects, these people tend to be more clueful than for others; also, for some subjects the culture of this group makes the useful contributors more likely to register than for others. When these two groups intersect, such that there are many clueful unregistered people tracking a specific article, that's when you get these high-quality anon edits.
Off the top of my head, [[Siamese Fighting Fish]] seems to be a good example of an article with many good IP edits and little vandalism. Presumably there are many others, but they're not the ones one usually encounters while carrying out admin duties.