there are no real disadvantages but you could argue that the quality is less than a cd(hardly noticeable - if at all) and that when buying a cd you get proper packaging
Proper packaging.
Not a physical copy.
If you believe the record industry that is out to make as much money as possible, you don't support them ripping off 40 year old songs and they can't bring in any new "talent." Maybe thats why programmes like Pop Idol exist.. Arghhh don't download!!
What Mattk says about the quality is incorrect. You can download mp3s that are recorded at 512kbps which are actually higher quality than CD. The 'normal' bitrate of mp3s is 128kbps which is near CD quality. Another disadvantage if you are downloading from P2P networks is the reliance on other people keeping their PCs on whilst you dowload. If they switch off, you get half a song and have to locate the rest of the song from somewhere else.
My son spent a lot of time downloading music and the disadvantage is that his computer was forever riddled with viruses, hijack programs, and programs that autodialled to premium rate numbers. I was for ever trying to clear his machine of these infestations.
before you download any mp3s make sure that you have a spyware program (Spybot) and anti-virus programmes running. These sites are notorious for downloading unwanted material and screwing your computer up.