About 10 days ago, there was an issue involving scans I posted on a community, namely a death list from a particular anime. What stunned me however, was that the scan in question was reposted on the community within 24 hours. Ordinarily, I wouldn't kick up a fuss about it, especially if the scan appears in a community or forum I don't and won't ever venture into (I even say so in my profile), but in this case, I was fairly annoyed, especially when it appeared again a couple of days later, courtesy of another person.
There are two different issues here, one perhaps more understandable than the other. Firstly, when posting something on a community, it is the poster's responsibility to check if it has been posted before, no matter how important and attention-demanding the scan, image, sound clip or whatever is.
(I admit that I wasn't particularly good at drawing attention to the scan (with good reason - I didn't want my email flooded with LJ comment notices) which is also why I simply asked the first reposter to credit me and perhaps link to the original post. I hate sensationalising things, but that's more my problem then anything else.)
The second issue is the assumption that information on the internet is free for all. Certainly, I scan and post things to be shared. However, it is common courtesy to respect a poster's wishes about the information they share. If no wish is explicitly expressed, then one should ask before posting it anywhere, if only because the original poster may not have wanted it shared in certain places.
One might argue, I suppose, that the scanner has no right to restrict the sharing of a piece of work he/she didn't even produce in the first place. However, that argument assumes that no effort was required on the part of the scanner. I won't go into how much time scanning and processing an image takes, not to mention the effort and cost of actually acquiring the material. Pages that are dominated by text may not take as much effort to scan, but what about obtaining it in the first place?
Granted, many of those who don't credit might not have gone through the rigourous drilling regarding proper referencing that any uni student should encounter. This, I feel, is an issue that needs to be addressed as more and more young people involve themselves in cyberspace.