If it is a long list then the O of the algorithm matters a lot.

If its a short list, who cares?

If you care about it all the time then you a premature optimiser - basically a hand-grenade with the pin out.

(by you I mean 'one' here - not you AdamT)

If you are implementing, than you are right. If you are interested in studying algorithms and how they work, asymptotic considerations can tell you a lot about the algorithm. You have to decide what you want to ask for in your interview.