Shareaza

I downloaded about fifty JPEGs with Shareaza 2.5.2.0 during the past two or three hours. I'm pretty sure they all showed a green Completed, Verified in the downloads window when done. Despite this, one of them appears to have been corrupt: Windows Explorer would not thumbnail it, the picture and fax viewer would not view it, and Photoshop CS2 would not open it.

That's not supposed to be theoretically possible, is it? If it shows Completed, Verified the file as received should be a bit-identical copy of the file as transmitted. The odds against a chance hash collision making a file seem ok that actually was corrupted are literally astronomical, even if Shareaza weren't potentially checking it with three or four differently-calculated hashes. SHA-1 alone, with 2^160 hashes, gives odds scarcely better than one in a googol of this happening.

On the other hand, the file obviously was corrupted in transit; there's no reason for someone to be intentionally sharing (or even keeping) a jpeg that is broken for whatever reason. (There are spammers sharing intentionally broken music files, but jpegs? And it had a single, fairly slow source and generally looked like a legitimate hit. Spams tend to be easy for an experienced user to spot and tend to have several sources and download, if at all, lightning-fast, since the spammers tend to have a high capacity server farm. Furthermore, the only image search spams I've seen in years of using Gnutella have been images that are actually ads, deliberately mislabeled as something else, or copies of legitimate images that have been altered to add an ad banner or similarly.)

This suggests the possibility of a bug in Shareaza's hashing, or that can cause it to skip the integrity check from time to time but still report a file as Verified.

Maybe it was corrupted when move from incomplete to downloads.

In G2 many corrupted (incomlete) files and spam that generates by your search request.

Attach one of broken jpegs here.

You downloaded a file that was already corrupt or incomplete. You have no evidence that the file you downloaded did not match the SHA1 advertised. Normal users do share bad files. If you are unwilling to provide any sort of evidence against a proven system, there is no reason people will believe you.

90% of all files shared in p2p are some kind "broken" files: stupid LW users shares partially downloaded images/mp3/movies as new unique files, some bastard change some metadata in big video file and we get two big video files, and so on
There even people that share utorrent temp folders: files with 1% of data in the beggining and the end and 99% of zeroes

Wonder how long before the "showstoppers" & "I WANT IT FIXED NOW" starts again

You were asked to attach example of broken file. File can be damaged also accidentally by virus or HDD failure etc. In such case Shareaza will hash damaged file. If you would found that file by name searching you will just download identical copy of damaged file.
And there is none reason to not share fake graphic files just like mp3 or any others. This is just your believe and not a proof or any rule.
Also would be strange if Shareaza would hash incorrectly just this kind of files. However this can be excluded only when you will provide damaged file as devs asked.

U don't get it.
I have file downloaded to 50%. I rename it (intentionally or not - it doesn't matter) for example to "gangbang.mp3" and put to my shared folder.
People shares tons of such files. 50% of all my download are holy crap - they put to .zip or .rar archive folder with multiple mp3s and sfv file to check them, but only 2 of 10 files pass sfv-check
I downloaded educational video, but after 32 minutes there are only zeroes, video skips to end credits.

Shareaza treats all files equally. Only for us humans it makes difference if this is mp3 or anything else. If you do not want to show your search then you can send this file via PM to Ryo. So you will obtain expert opinion, I think. This could be a bug, but we will not find out this theoretically by posting here. However that would be really strange bug IMHO.

My guess is that this is spam. The spammers are taking a few files and listing them in search results under different names. The file probably is not even an image, possibly a zip file. If this is the case then it makes sense that these files would have other sources from people who accidentally fell into the same trap you did, and forgot to delete or mark the file as fake/spam. Fakeaza/shareazaV4/5/6 does not even use G1/G2/ed2k they use there own centralized network, but that doesn't mean they are not spamming our network.

Recently downloaded movie file without some parts filled with zeroes - another user share his uTorrent downloads folder.
Also have .jpeg renamed to .pdf.
There are thousands of examples.

Some group of pirates release some movie. Many bastards edit their release: one bastard removed half of end credits, other remove something else, third edit some metadata - we have many different files/hashes of same movie: one original with 100 sources, second - edited by bastards who doesn't understand how p2p works - with 12 sources and many others with 1to2 sources.

While writing this downloaded .jpg without 20% of picture missing in the end.

Those are still usable (or partly usable) files. The files I'm seeing are ones nobody would have any reaction to on downloading them except to delete them or even mark them fake/corrupt. If, per your hypothesis, someone got and is sharing such files, why didn't they delete them? Nowhere is there a fake/corrupt rating for these files either. It just doesn't make sense that it's anything but in-transit corruption.