With so few people actually scanning anything around here, it seems a little silly to suggest that there's a standard scanning size being used, because there isn't. If a couple of people use one size and a couple of people use a different size, then there is no standard. However, our scanning rules HAVE set 2200px high as the minimum size allowed (I'm not sure how that particular size was arrived at), and there are some people who release their scans at this size.
I go bigger, although I have yet to go full 300dpi. I usually release mags at sizes between 2500-2800px high, and I even released one at 3000 once (300dpi is usually in the 3200-3300 range. But I feel in some cases it's necessary, and here's an example of why.
Areala asked me a question recently about an ad I uploaded, and while looking at it, I noticed that some of the fine print was illegible at the size I had uploaded to the gallery (2200px high, the same size as many of our magazine uploads are released at.) I still had the 600dpi scan, which was of course quite readable, and I also had the page as was edited for the magazine upload, which I had saved at 2700px high and was also readable. So in this case, 2700 was OK, but 2200 was not.
From top to bottom, 2200px, 2700px, 6100px. Please note the kanji pointed to with the arrow. Anyone fluent in Japanese would still be able to read the top pic because of the context, but for anyone else who actually needs to clearly see the lines of the character (raises hand), the 2200 scan makes this kanji become a bit of guesswork. The 2700px pic is totally fine, albeit not as sharp as the 6100px 600dpi scan.
Now, it's true that this is fine print, and isn't anything that a normal reader would even care about. Indeed, it's small enough that it's pretty damn hard to read when looking at the actual magazine page. But this example DOES prove that 2200px isn't up to the task of capturing such fine print.
I'm not saying we have to bump up our minimum scan size, but I would at least encourage anyone scanning something to make certain that everything in their scan is legible at the size they save their edited files at.