Because the networks Shareaza uses are entirely decentralized (except for BitTorrent), so anyone can put any file on the network, you just can't censor anything. The result is that there are folks who rename their files as a joke and there are spammers too, trying to flood the network with malware (Trojan horses and such) or multimedia files infested with Digital Restrictions Management (DRM) so that they can "suggest" you to buy the rights for the file, or purchase a totally unnecessary codec, when the so-called "codec" is not some kind of Trojan horse itself.
These spammers also use bots which reply to your queries on the fly. Just try a search with mskjfqdfsq, you'll probably get results.
How to fight that spam? Shareaza already filters a good amount of that spam with its built-in filter, but needless to say you
should have an antivirus program installed. Avoid downloading executable files unless you're
really sure that they're clean (using a magnet or ed2k link from a trusted site such as
eMule's Content DB), check your files on Bitzi (right click on search results then Web Services and then See Bitzi Ticket), pay attention to other users' ratings on Shareaza itself too, especially to negative ratings with actual comments (spammers tend to rate themselves with the perfect score). You should also always limit your search to the right category (audio, video, archives etc) and provide a size limit (most malware tend to be small, less than a few Mbs).
Finally, to fool the bots that reply to your queries on the fly, rearrange your keywords. Say you want to download
Tales from the Public Domain BOUND BY LAW.cbz, you should type something like Bound Domain Public Law from Tales. The answers replying with that order would obviously be spam generated on the fly, therefore you can disregard them.
Hope this helps a bit.