Everybody, including the people who wrote the summary are treating patents as if they were perpetual - but they are not.
AFAIK the really good patents (about the FAT-filesystem) are expiring 2015. There are still some shady non-essential FAT-patents that expire IIRC until 2017, but those are easily worked around, have tons of prior art, are about non-essential features and/or are laughably frivolous.
So of course a patent-portfolio purchased in 2011 may be worth a lot less today. It may be even worthless, depending on what patents have expired. Basically the worth of a patent portfolio can be calculated by how much money could be milked so far (by royalties or monopoly pricing) from it multiplied by the time still left until expiration. So most patent portfolios will lose value over time (although there may be rare exceptions when some revolutionary products come out - but that did not happen since 2011).
People, do you remember the gif-pdf patent outrcry? It's ancient history now - and all these patents will be history in just a few years because most of them were filed in the 1990s.