Question to those who assumed the schema would be more complicated: Why? Maybe I'm not as good with DB design as I should be, but what parts of Wikipedia did you assume would garner more complexity? Their data layout is pretty flat and I'd actually be surprised if it was more complex than this diagram.
Often, simple growth in a company will create a messy schema. Version 1 is often clean, but as you iterate and more functionality is added, the schema often undergoes a hideous transformation from museum-piece to something not that.
I personally expected Wikipedia to have an uglier schema because of hacks they would have to do for performance issues. I expected a lot more denormalization and duplications.
