Some people compare this mechanic technology with a lottery because it could fail any day, any moment. There are server-based scenarios where different individuals were making statistics about brands and models, with a 24x7 operation. Some do not resist specially well and week after week the number of faulty HDD drives around the globe continues growing fast.
The warranty period expires and well, you have another brick to use for equilibrating a table or something. The data could be there, but who cares? Another example of a good investment and it makes you more willing to buy twenty more.
However, it suggests an interesting question about the importance of providing more storage or a more reliable technology that last longer, up to a thousand years. Nature goes even longer sometimes. Although perhaps like those random algorithms, the most relevant part of the analysis —representing the units working more than 20.000 hours— seems to go in a controlled fashion even if the faulty units appear to some. We hope the SSD technology or others allow a better and fairer reality.