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While I'm certainly not engaged in any form of blackhat techniques, we were severely affected by Penguin.  Needless to say, we suffered a 50% drop on April 24 and have not risen back since.  For that reason, yes, I do have link paranoia - good term

I'm thinking of making another post on the subject (YouMoz) because I've finally figured out what happened.  I'm hoping this next update will catch my fix.

For the record, they are not spammy but rather topical sites and directories related to Ghosts or New Age stuff.  Again, we have nothing to do with these topics.

Seems like the consensus is just leave them.  There are about two dozen out of 2000 links I manually reviewed in a spreadsheet.

Strangely enough, I once owned Presonus audio equipment so I felt I thought I should chime in.  In my experience, people certainly type in specific version numbers for products.

Consider software downloads.  If you're looking for a particular build of FireFox, you'd search for that.

Another example would be digital cameras or product number of parts for home electronics.  Both are items that I've typed into Google.

My guess is that Google is compiling data from both type-ins as well as "known" product numbers from page titles, links and more likely product feeds.