There's no way that anyone from LW can control what's being shared on the Gnutella network...it's p2p. Users connect to other users' computers to download. There are lots of organisations whose aim it is to sabotage p2p. There's more info in these links.
Recognising Fake files
autogenerated mp3 spam results


So, yes there are heaps of infected & spam files around but there are a few things you can do:

Use the junk filter.
Pay attention to file sizes...if a file looks suspiciously small then avoid it!
Use the keyword filter to filter out common spam-related words (eg pranked).
How to add words to the filter
Keywords worth filtering

If you're using LW 4.13 or later, try applying the hostiles list. Click below for more info.
The TechNutopia Fullsize Hostiles List for BearShare and LimeWire