Sealed un-sucked
A marvellous nugget of comedy PR from the "Implementing Singleton in C#" section on Microsoft's Enterprise Patterns site:
[Sells03] Sells, Chris. "Sealed Sucks." sellsbrothers.com News. Available at: http://www.sellsbrothers.com/news/showTopic.aspx?ixTopic=411.
Note: Despite its title, the "Sealed Sucks" article is actually a balanced discussion of the pros and cons of marking a class sealed.