A few days ago I wanted to check out an album. After dl completion, I've copied the files onto my ipod and begun listening. I really liked it, however I didn't find one song that was promoted as the 'headliner' of the album. I deleted the tracks and started a new download, with better sound quality and, as I suspected, some songs that were missing. This time all the songs were completely different and I did not like them. The strange part is that both albums sounded like they were made by the same artist, though when I checked out all teh songs on youtube, the latter versions appeared to be the true ones.
Now I don't have any clue what I was listening to on the first time.
My suggestion is to keep a dl/search log that would be arbitrary and for personal usage only. It would be more permanent than the download library - It's too easy to delete stuff from there.
The info that would be kept there might include
-the user from whom the tracks were downloaded
-date of dl request & completion
-other (I haven't thought of any so far)