The rule of 7 states, it takes 7 interactions with your brand before a person will engage with it and become a client or customer. 
Originally it started as a rule of 6. In 1859 The Weekly Constitutionalist from Augusta Georgia describes the rule of 6 as,
“The first time a man sees an advertisement, he takes no notice of it, the second time he looks at the name, the third time he looks at the price, the fourth time he reads it, the fifth time he speaks of it to his wife, the sixth time he buys” 
The seventh rule was added in the 1930’s by the film industry. Studio bosses found it took seven impressions of advertising or promotion to make people see their film. 
Is the Rule of 7 still applicable in the era of Google and internet searches?
Yes and no.
Putting aside the sexism and quaintness of the 1859 quote, obviously the Rule of 6 is no longer relevant in the 21st century where social media affords organisations and businesses the opportunity to touch the lives of clients more than 7 times in a day. Old school marketing is crushed by a medium clients are engaging with multiple times daily. 
However, the underlying principle of the Rule of 7 that organisations and businesses need to engage with clients does apply. This engagement must be more strategic and targeted than ever before because of the sheer volume of advertisements people now see. In the 1970’s the average US customer saw an average of 500 advertisements/day, but 2017 the US customer sees on average 5,000 ads per day. 
Given the importance of social media to clients and customers and the sheer volume of information that is being received by them each day, how do organisations make their brand stand out?
Social media savvy organisations know the importance of having a thoughtful content strategy to engage clients.  A thoughtful content strategy has three principles, like a three-legged stool.
The first principle is to know your client. Do you have a clear profile of who your clients are? Their interests, their concerns, the problems they are seeking solutions for. Or when you think of your client is it just an amorphous group of people? A thoughtful and thought-through content strategy begins by knowing the specifics of your client group.
The second principle is to make a connection. Tell a story that creates an emotional connection. Despite the fact we think we make rational decisions, buying and engagement decisions with companies and organisations are often shaped by two things, the stories that are told and the memories the stories leave.  We need to think about ways to engage ethically when creating emotional connections with clients.
The third leg of the stool is to provide a solution. Providing a solution is also about providing information and content that is useful to your client. This third principle is closely linked with the previous principles. To provide a solution, you need to know what your client is seeking a solution to. In other words, you need to know your client. The solution should provide information and content that “delights” the customer in that it is helpful and of benefit to them. This assists in building the emotional connection to your client, which is the second principle.
The fundamentals of the Rule of 7 of the 1930’s still apply in the 21st century, but they apply with a twist because of the nature of social media.