Traditional marketing in consumer products e.g. retails, probably focused on age group. For example, in cosmetics, usually the firm would focus on certain age group. But when these group of customers aged and passed their target age group, they will have to find new customers of that age group to replace the existing ones.. As we all know by now, it's expensive to find new customer than maintaining existing ones.
Now comes Harry Potter marketing. It's a new concept following Harry's success. The concept simply follows the customers.. in the cosmetic example, the firm's brand/products should grow 'old' with the customers - shaping the marketing message to suit the aging customers. For example, in the beginning, it could be targeting customer in their 20's. The message would be on skin whitening and smoothness. But when the customers reached their 30's or 40's, the message may be tuned to focus on retard aging and skin maintenance.. The product composition will have to be adjusted as well..
The pros are that it grows with the customers (which u probably already know them well) and save money to find new customer (existing customers cheaper to keep).
The cons are that product/brand will grow 'old' and die off one day and new customers who dont belong to that generation will unlikely to be your customer.
In a nutshell, Harry Potter marketing is an interesting new marketing concept which is suitable for certain products/services only. It will not be suitable for, say in the machinery equipment marketing, or even Walt Disney fixed target on children. Alternative marketing strategies would be to develop product lines or brands that carries the customers from one brand maturing to another brand thru the use of clever marketing creating a seamless transition unconscious to them.. but that's another discussion or topic.. ;-)