If Google decided to charge users for Gmail, what would be the impact? Should it proceed to charge users for using Gmail?

Approach:

I would ask a set of clarification questions to understand the problem better and then establish the goal that we try to achieve.

I would assess the business impact of the fee for gmail service and make the recommendation accordingly.

Clarification questions:

Candidate: Is the goal here to maximize the revenue or long term free cash flow for the company

Interviewer: Yes

Candidate: Are we planning to charge for the service only in the countries where gmail market share is high or WW

Interviewer: WW

Positive impact of charging the fee:

A) Generate incremental revenue: In addition to ad revevenue, fee will create a new revenue stream that will maximize the long term cash flow for the company

B) Entirely stop gathering user information for advertisement, allaying the privacy concerns for customers: For all the paying customers, we will stop collecting personal information for the purpose of serving ads. It will address the privacy conerns of the customers.

C) Ear-mark the incremental revenue to fund moon shot ideas to further improve the gmail service: New revenue stream will enable google to take a long-term view and fund resource intensive initiatives such as offering video calling capabilites on gmail without any user limit, offer more customization features, etc.

D) Less regulatory scrutiny: As google move away from ad model and stops collecting private information, it will lower the regulatory scrutiny from the governments.

Negative impact of charging the fee:

A) Losing price sensitive customer base to competitors such as yahoo that still offer free service: It will be biggest consequences of the price increase. Pain will be more pronounced for the customers in the developing countries that cannot affor the fee.

B) Negative perception and bad PR: It will create massive backlash from the customers, and create a online compaign to delete google apps

C) Loss of access to key gmail information  will negatively affect google's ability to offer other services such google assistant and loss of gmail customers will also negatively affect the customer engagement on other services such as google calendor, google meet, etc. 

D) Value of google ecosystem will take a hit, as customers quit the platform due to fee. 

As the disadvantages outweight the advantages, I would recommend against charging the fee for gmail.