Quote from the movie Constantine: "They call it the balance."
Balance and flexibility are key aspects when trying to enhance a particular QR Code. Changes to the default graphical appearance could throw the complete code off balance, rendering it useless.
Flexibility with regards to the rules and boundaries that define a QR Code can change a one in a million QR Code into the one out of a million.
The balance and flexibility are also needed when running an advertizement or a marketing campaign.
Be flexible to make your product or brand appealing to the right audience, change and adapt when needed.
Create the right balance between changes and sticking to your product or service, if you change too much, you might end up raising the wrong expectations.