For brands, engaging with the consumers after-purchase to drive loyalty and repeat purchases is often more profitable than expensive acquisition of fickle consumers (a la Groupon). Customer service is not usually the best place to start an interaction, but if handled well, it could be a strategic tool to increase loyalty and brand advocacy. You might even agree with the (provocative) statement ‘Customer Service is the New Marketing’.
Some early adopter retailers are beginning to do this (beyond coupons & deals). It may be even more important for consumer products manufacturers that are disintermediated from the end-consumers. Mobile gives them a direct engagement channel - not just to reduce costs by self-service, but to know who their consumers are (which many don't know, as few customers register) and get insights on how they use the product.
Mobile does introduce many challenges. There are only very few successful examples of engaging brand mobile apps (such as Nike+) with high customer adoption. It might be partly because of the app fatigue ('download yet another app!') and probably because of the pushy sales approach without offering much value to the consumers (the same reason why many brand Facebook pages struggle).
Today, Most of us are happy (or at least, got used to!) going to our computer and Google (or Facebook) for any customer service issue. However, just like any digital consumer interaction, I believe customer service is moving to mobile too, if it's designed well to deliver value to both the consumers and enterprises. I am interested to hear what you think.