Even though iTunes will be going DRM-free through iTunes Plus, your information still isn’t private. Your e-mail address is still associated with the songs that you purchase and download on iTunes, despite being DRM-free. So you can share your music with friends and family, but make sure that they do not end up on file sharing software like Limewire or Mininova. Because the songs will be able to trace you down.
To check to see if certain files are yours, open the iTunes Plus file on your computer using a text editor software (such as Notepad). There will be quite a bit of gibberish in the file, but do a CTRL+F (Find) and search for your email address.
iTunes use files that are AAC, not the usual .MP3 type. Although some music players support this format, others may not. Fortunately iTunes can convert the AAC/.M4A files into MP3. iTunes has already started supporting DRM-free songs with 256 kbps quality.