Depends of a product, Useful in political marketing, when mass media can't persuade the mass public. If mass public has no interest in product or service (politics included), do door-to-door campaign.
The hardest door to open is your car door.
It was the hardest job I ever had, the most fun when money is being made, the worst ever when I had a bad week.
As with all sales, 20% of the employees make 80% of the money. Reality is 5% make 70% and the rest fight over crumbs.
The best part is that you make exactly what you are worth.
Measuring the effectiveness of door to door marketing depends on several factors. A highly skilled sales person will be more effective than one who is just starting out. Failure is very common in direct advertising, and it takes an extremely motivated and tenacious person to be able to persuade in this manner. Please also note that because of "No solicitation" signs are increasingly common, territories for door to door marketing are more and more limited.