Reasons for doing this:

1. We benefit from the existing test architecture (currently it's very difficult to test wiki doc stuff without clobbering the transclusion index)
2. We benefit from load balancing /doc against all servers
3. We simplify our hosting configuration due to point 2
4. We simplify our codebase to just do normal inserts and selects, rather than having to maintain a flat file database.
5. We can replicate this to slaves so they have working documentation