1. MySpace: The ugly stepchild, the target of everyone's affection. It's anarchy of customization, Photobucket widgets, audio, and image backgrounds is gut-wrenching and mind-numbing. It's also it's most distinguishing competitive advantage. Beyond MySpace's personalization features, many of its core features go unused or are poorly designed. Grade: C- (inflated from F because it wouldn't be MySpace otherwise)

2. Facebook: The antithesis of Myspace: crisp design, limited customization, focused feature set. Grade: A

3. Bebo: (Nielson has particular reservations about websites chasing the usage pattern of teenagers.) Somewhere between the crisp and functional Facebook and the chaos of Myspace lies Bebo. It satisfies its community's heartrending cries for individuality while remaining functional without inducing seizures (most of the time). Grade: B+ (for having some class while still appealing to the teenies)

4. Twitter: Focused on the core functionality of the service with limited customization of backgrounds and icons. Because it is primarily a service, the web site is often circumvented entirely by widgets, client apps, or mobile devices. Grade: A (for its avoidability)

5. Geni: The genealogy-focused social network deserves special mention because without "chasing Web 2.0", it would not be possible. It's primary interface, building family trees visually, is dependent on new Web technology and customization. It's a shining example of exploiting new technologies for new purposes. Where it is subject to criticism is its lack of greater customization and viewing options. Grade A+ (but it could use an upgrade)

Conclusion: Design always has its examples of good and bad, and most are in between. Even a good design is worthy of criticism. However, the state of web sites is no different than at other times. New technology is exploited for functional purposes and can be over-used. Customization can interfere with the user and get out of their way. Teens are the target demographic of most every market. Jacob Nielsen would have less of a foundation on which to base his criticisms without everyone's poster child, Myspace, but critics will always have a job.