[geocar]

Yes. It is occasionally useful.

However when you have the right data structure, you'll find you won't need it.

Benchmarking is important because searching for the right data structure is time consuming (expensive for the programmer) and it's usually not necessary.

[DanWaterworth]

When you need that kind of behaviour, you can't replace it with something flat (without doing binary searches or similiar at each crossing). Sometimes intrusive lists are the right thing.

I built something once that used intrusive skiplists because it needed to expire elements using one ordering and search them by another. It would have been much less efficient if I'd have broken it up into multiple flat representations.

(Actually, it was flat, but explaining that aspect of it is quite difficult).