>I agree that computers "don't get slower", they are always the same speed as the day you bought them, that software "doesn't get worse", it's the same software as the day you bought it. I get the comparative nature of this.
This is true, but at the same time growth in data sets can make this not true too. Start out with a customer database that has a limited number of fields and it works great, everything hot fits in cache, most of the database fits in memory. Then as the years go buy you need to store more information. You add more columns, for things like email, websites, whatever else you can think of. All of the sudden your it doesn't fit in cache and you get a dramatic slowdown. You decide to live with it rather then spend $10,000+ to upgrade. You add many more customers, now the data doesn't fit in memory and you're going to disk and swap. I see this happen in real life quite often with large companies that take 10+ seconds to look up customer records.
Software doesn't change, but data does. And the data makes or breaks the system.