Always. I don't think this tradition or business courtesy has been modified. Hell, I still wear a full suit to a wedding.....even though things have changed in that arena. I think it just comes down to courtesy.

It all depends on why you are resigning. That's a touchy question.

From what I've been told. A two week notice is not necessary but for me it is. If a company took the time to hire me and put enough faith in me; then, the least I can do is give them two weeks in order for them to find a replacement.

Absolutely