Apple Insider has a thoughtful article on market disruption in the context of Apple products. Most interesting to me was how they broke down market disrupting products into 3 categories:

• New Market Disruption: create a new product that no one knew they needed
• Better Product: disrupts the high end of the marketplace by bringing new features that drive customers to upgrade
• Lower Cost: disrupts the low end by decreasing the cost for customers who are already serviced in the marketplace

Their observation is that grabbing the low end is easier, but not necessarily more valuable. Apple has succeeded when they take new markets and make better products, then fill in the low end eventually.