Nope. The single largest bitcoin balance in an active address is (very probably, not offically confirmed) the internal mixer address for Silk Road. Satoshi Dice has a long way to go to catch up to them. Technically, however, no single person "owns" that address, and the value is possessed by a large number of users and dealers on Silk Road.
EDIT: I meant to say pool of addresses, the mixer doesn't untilize a singe address, but a cascading set of addresses. MtGox's internal wallet service works similarly, but the mixer does deliberately move balances out of and back into the pool in complex ways. The paper this article refers to fails to consider the existance of this, and other, coin mixers that exist to hide the origin and destination of transactions. The one at Silk Road is almost certainly still the undisputed king of mixers, but others also certainly exist. R & S are more likely lesser used, and less well known, coin mixers.