Think it means that most machines are not memory or disk constrained these days, but there is extra processing to perform the dynamic linking. Sort of a cost-benefit argument it seems. Doesn't address the issue of security etc and the benefit of just having 1 instance of a library to update when maintaining a complete system however.
[I should not have brought shared libs into this, I now regret it, because it sidetracked the entire discussion, but...]
The extra processing is more significant than most people think. The library has to be compiled as relocatable code, which incurs a runtime performance penalty. You also lose a register, which especially on register-constrained architectures is really bad (it was a tragedy on iA32, it's less of an issue now).
