Google's Director of Staffing Progam says that even in her digital world, a handwritten "Thank You" note is best

In today's world, e-mail has replaced snail mail as the preferred mode for much communication. But etiquette expert Ms. Post and Judy Gilbert, Google's Director of Staffing Programs, both agree that a handwritten note is still the best way to say "thank you." 

A real-world business anecdote:

The President and CEO of a small but thriving business didn't hire a high six figure salary candidate because that person didn't take the time to say "thank you" for the $150.00 business lunch, the hour of the President's time, or the introduction to his company's most important clients. 

In such cases, Judy Gilbert says "thank you for the meeting" or "thank you for the conversation" is both appropriate and necessary.

And this from the Jessica Liebman, Managing Editor of Business Insider:

I'm the Managing Editor of Business Insider, which means I'm responsible for all of the editorial hiring here. So I'm constantly meeting people of all different levels, from interns to senior editors.

Lately, the majority of people I interview have one mistake in common.

They're all messing up on something that I think is very important when trying to get a job: the "Thank You Email."

Whether we spent thirty minutes meeting in the offices; we Skyped because you're abroad for your Junior spring semester; or we did a quick first-round phone interview, too many people are forgetting to follow up later that day or the next day with a quick email.

It doesn't have to be anything too involved. Truthfully, the shorter the better.

The "Thank You Email" should say a few simple things:

-Thank you for meeting (or talking) with me.

-I really want this job.

-Quick plug about why I'm perfect for it.

If I DON'T get a "Thank You Email", here's what happens:

-I assume you don't want the job

-I think you're disorganized and forgot about following up

-There is a much higher shot I'll forget about you