Can I download pirated songs and songs with unknown sources to an Ipod?

I am considering buying a Ipod touch. Was told by a friend that he was not able to load some songs from his pc to the Ipod because they may have been pirated or had unknown sources. Along with music cd's I purchased, I have pirated music, music emailed to me by friends where I don't know the source, and other unknown music sources. If this is an issue, is there a way around it? Any info will be greatly appreciated.