Does wikimedia currently use MySQL enterprise edition or community edition?
wikimedia uses four-oh-forever ;-) (4.0.40, in-house fork), though some servers are still at 4.0.26.
there is a plan of going up to 5.0, with incorporated innodb scalability fixes (announced by google at mysqlconf a month ago) - that way we may go after far more evil sharding, and with better data locality - after full 8-core boxes CPU load. in theory. :)
BR,