From Seth's Blog:
It's okay to treat some customers differently, but first it pays to figure out who you're dealing with and why you want to re-allocate your resources.
I'd go as far to say it's impossible to treat all customers the same even if you wanted to. Customers who contact your customer service are getting 1-on-1 service that the others aren't.
Just be honest why you're treating customers differently. Because they had a problem, because they paid us the most, or because they are the loudest are all valid responses.
Eric Davis
How do your products determine customer behavior
In Repeat Customer Insights the Customer First Product analysis will measure customer behavior based on the products each customer first ordered.