I think this is the biggest one that many people don't realize. Not that they aren't good programmers, it's just that so many things are I/O bound, nowadays.CPU cycles are a precious commodity and your programming style and language reflects that belief.
There are plenty of problem domains where you have to worry a lot about CPU cycles (modeling/simulation, signal processing, OS kernels, etc), but you don't work in them. Like nearly every software developer, your biggest performance problems are all database and I/O related. The only effect of optimizing your code for CPU is to shave 2 milliseconds off the time to get to the next multi-second database query. Meanwhile your development has slowed to a crawl, you can't keep up with the rapidly evolving requirements and there are serious quality issues. But at least you’ll be saving lots of CPU cycles... eventually.