A few people have said that when you plug in someone else's iPod on your iTunes it wipes all the other songs off is this true. If it is can it be prevented in any way?

If you plug in there ipod to you pc with your itunes it is possible that it will wipe there ipod n use the library thats on your pc lol

Well thats for that I hope your sure now I'll go and try it

sure it doesnt wipe the songs of your computer,  bcos ipod sync's with itunes. not the other way around usually

Possibly YOUR IPOD looks for the matching songs/vids/etc. on THEIR PC, but doesn't find them, and so it says, "these songs must be corrupt, even though I have a copy of them on me. I'm just going to delete basically everything for no valid reason at all."

And vice versa (THEIR IPOD, YOUR PC). I have no idea why that happens...whoever coded that may or may not have been paying attention.

just make sure the ipod sync option is off before you connect it

If it isn't sync-ed with that computer, it will usually ask you what you want to do. 

When I connect my ipod to a diffrent PC it asked me if i would like to wipe my ipod of all mucis ect.. and then sync with the itunes libary on that pc. i just clcik cancel. but it's very anoying. so if you just selecs cancel you should be ok!!

Ok thats good thanks.

iTunes 7 will prompt u for the sync, just click on cancel, on the devices section the iPod will appear and you'll have the option to sync this time (or resync), u'll also have the option to manually edit the music inside, and there's no way to shut it down for the first time use 'cuz they took it out of the preferences pane.