Since users publish data into CDDB it is pretty normal to find multiple listings for the same (commercial or otherwise) CD. Further since record companies sell their album images to other companies to resell and otherwise distribute and package them differently for different markets - two users may correctly enter very different information about the album. For example I bought a classical music collection and about 1/3 of the CDs come back from CDDB as being a completely different collection - the same composers, orchestra, date, location - but a different record label and different collection title; for some of the CDs entries exist under the name I know and another name, for some CDs only one or the other exists and for others there are many entries.
I prefer it to entering hundreds of albums worth of data from the cover - this is all just stop gap until pay on use becomes competively priced with sufficient coverage (pay per play for pop-100 would be worth it for me, but would not deprecate the need to access my personal media collection most of the time).