This is an interesting article, simply because people criticise Googles goofy questions when in fact they are very revealing as an assessment of the candidate..

My Nightmare Interviews With Google (GOOG)

15 Google Interview Questions That Will Make You Feel Stupid (GOOG)

The fact is that on one level google is interested in your GPA score (whatever that is, obviously like the US SAT numbers in school quals) which shows you can rote learn.

Then it’s interested in how you can use deductive rational logic to assess questions in a reasonably unstructured environment.

Furthermore the additional twist when trying to make the questions relevant to the internet and online advertising detects if you really have a passion for the business.

So, let’s critique what she said...

"I googled Google and learned their history, products, current news, founders, locations, business models, competitors, AdWords, investors and mottos".

I don't really go for that, IMHO if that’s the differentiating factor to decide whether you get accepted for that company, then that company doesn't really want intellect. The real learning about Google is you developed websites or were into being a domainer.

"“I want you to estimate,” Oliver began, “how much money you think Google makes daily from Gmail ads.”"

This is an excellent question. They aren't actually that interested in your actual quantifiable answer (In fact the interviewer most likely does not even have the answer written down (Google probably doesn't even know themselves with any great deal of accuracy - I've heard about their revenue recognition systems) I guess the interviewer might have been given a very rough ball park figure as being an HR person they aren't the brightest of sparks, and think an answer of 10 billion is a reasonable
number )

“Google places four ads per e-mail opened in Gmail. Advertisers get to pick their click-through rates, which can be as little as $0.05, and they can set a maximum daily charge, which can be $5. The amount of money Google would make in a day would depend on the number of Gmail users, the number of e-mails those users receive and open per day, the number of advertisements they click on, and the rates the advertisers are charged.”

Ok, the advertising model works like this.

Advertiser -> Google -> Publisher
20c -> 15c -> 5c

However as Google own's GMail they are both Intermediary and Publisher.

For this question Google would not care how much Publishers get, because they are the publisher and the intermediary (The $5 limit etc just shows the candidate knows absolutely nothing relevant - Its a straight out blurb from the adsense sign up for advertisers, For any calc only the total advertising dollars of all advertisers matters). The figure that matters is how much the advertiser would pay for an ad (And if there were enough ads to serve). This in turn depends on the type of ads served. Gmail accounts are more mainstream and most ads will be "entertainment" type ads, so the rates per click won't be at the level of financial services etc. Probably around 20c US (Which they would normally pay a publisher on a third party site a crappy 5c ). So lets stick with 20c. Google has dropped the minimum bid levels to zero I believe so just maybe email ads are really lower than 20c..

Click through rates

"If they click on ¼ of those ads"

This is where the candidate seems to have hit a flag. Given the interviewer says "You lost me at the ‘only clicking on ¼ of the ads’ comment" I believe that the interviewer was probably looking at his score sheet and that 1/4 was far higher than what was written there.

Click rates are really low in highly repetitive sites (That you have visited often). On email, they will be low, really low. A good website can do a CTR (Click through rate) of 5-10%. A direct navigation URL can do up to 30%. But email will likely be down in the 0.5-1.0%. This is per page, and not per advertisement block of ads. One email, one page one lot of 0.5-1.0%

Number of pages and users.

This is one is really difficult. Lets say 20 million users (worldwide) and 1 page a day.

So, I'd get a number of 20m x 1% x .20 = 40k a day or 15m a year approximately. Doesn't sound much but given that I'd assume Google’s PE is likely something around the 50-100 range (Need to Google that) then it ads a lot of value to the company.

Right or wrong, who cares other than you can step through the logic and show that you understand the industry, and have a passion for it (as you don't get this by reading their corp website)

And while the candidate can criticise the HR person, the candidate is applying for a role as "Associate Product Marketing Manager" so this is the basis for everything they do.

Nb: Here is the winning candidates interview answer....