Usage is great. My question would be for what purpose? For research and discovery, for social purposes i.e. facebook... myspace. Talking about purpose..Not too sure of the purpose of identifying various ethnic groups that are using the internet... Well...from a "marketer's" perspective - I guess it would be great to know in order to determine if the internet would be an effective tool to connect with your targeted audience.
Your final comment is correct. Marketing is more of a target sport, and knowing the proper sales channels to reach your customers is essential to the success of the product/service. In many ways, online marketing has the potential to influence other forms of marketing, due to the ability to collect relevant purchase decision data.