Speed, speed, speed....
Looking for data in a WebDNA database and displaying it on the page is faster than using static html pages with apache.
This is because templates as well as database content are loaded from RAM. The speed can only compare with cached static html files. Other dynamic content solutions will need a disk search to retrieve the database-loaded page content, but not WebDNA. Navigate this site, built with only two templates and one database, and you will see what I mean by speed.
Almost all other database systems are based on a disk-centric model, hundreds of times slower than a RAM-centric model. WebDNA writes individual changes to the RAM image of the data and a separate process maintains a current copy of the RAM data on the disk, within your site hierarchy. You can directly backup, upload or download your database content anytime, using ftp, and manipulate it using Excel or equivalent. You can also encrypt it if some data is sensitive.
Further, you are not limited by the number of databases you can create, nor by their size.