My Apple ID used to have a long list of products associated with it. They displayed in Apple's Support Profile.
Recently they all disappeared.
I found them associated with an obscure Apple ID (AppleID) of mine that I unwittingly created a year or so ago when registering for the dev program. I've never used that Apple ID for any product registration; I barely remembered it existed.
I have a theory as to what happened.
About two months ago, to deal with a very obscure MobileMe/Mail bug, I moved an email address from one AppleID to another. I suspect the product report was tied not to the Apple ID, but to that email address. (This suggests Apple is tying together the iTunes based AppleID records to the Mac purchase records by a 'join' on an amail address.).
I haven't tried moving the email address back to my original profile, I'm worried I'll lose all my purchase records. At least I know where they are.
I'm not optimistic that Apple will fix this problem, I've seen a range of Apple ID associated problems over the past few years and, if anything, things seem worse lately.
In any case, if it happens to you, try looking in foreign profiles. And be very careful of moving email addresses between AppleIDs.