[eluser]Colin Williams[/eluser]
I've thought about this before, too, especially with my experience developing against Drupal in which everything is a "node." It makes sense for something highly plug-able and extensible and open-source, like Drupal, but it also pays to be specific, like richthegeek pointed out. If everything in your app is an "item" in this monolithic "items" table, then all you've served to do is shift database-level complexity to table-level complexity. You have moved from a database where not all tables are used to a table where not all fields are used. Should you take it a step further, you could just have one table with one field that holds serialized data (which, I believe, is how Digg works...), or maybe just one included file that holds a massive serialized object....
