The way these two generations use e-tools and perceive two realities - online and offline - are extremely different. As a rule, "digital natives" view both realities as almost equivalent. They connect, chat and communicate with each other online extensively and these activities (the virtual world) have become an inseparable part of their lives. Meanwhile, for "digital aliens" like myself, online tools are merely a means to agree on the place and time of meeting with friends and colleagues in the real world.
The habits of "digital aliens" however change towards increasing digitalisation. Social-networking websites become popular not only with teenagers but with grown-ups too. For personal contacts and use, you may sign up with MySpace, the biggest social site, or Facebook, the second largest but apparently currently the "hottest" social network. There are a number of other social networks on the web, either of national reach or "multinationals".
Social networks may also be used for business purposes. The Economist, the business weekly, confirms that such websites do have business uses, including marketing opportunities. For example, I use LinkedIn, an online network for professionals, which has over 10 million users.
You may ask: why should one "waste" time on any of those social networks? Well, first, it is a fast and cost-effective way of maintaining contacts with your friends or colleagues, who may not necessarily be reachable by car.:) Second, it's a means of making new business contacts. I've used LinkedIn for such purposes and it has worked for me.
Of course, if you spend too much time online and get the feeling that the whole afternoon or evening has disappared, it's time for you to ask yourself: "Do I have a fulfilling first life?".

Manhattan network, New York City, July 2006. Photo by Giedrius CP