I am not in the habit of getting programmes off LW, for the very reasons you mention. There are hundreds of posts in the forums on Viruses, and I think half the trick is to be able to tell from looking at a file if it is good or not .. that only comes with the experience you are gaining downloading the bad ones!
Do a search on Virus in the forum and make sure your anti-virus software is up to date.
There is talk of a size filer and a spam filter being incorporated, and things are improving in this field but as Gnutella is a p2p network, I don't think it will ever be possible to stop viruses getting through or showing in searches 100% as you could in a server based system.
If you want virus free software go out and buy it from a reliable shop. If not take your chances and make sure you use the protection
