For the average player, sure. But for large organizations pushing the RWF, it absolutely is. These organizations have the liquidity and the ability to conduct sales runs for gold and remain above the board on paper but only a fool would believe that all gold in WoW is generated from non-RMT sources.
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Blizzard doesn't seem to care too much because the race is dictated entirely by the community. The only way I could see BoEs going away were if Blizzard officially sanctioned the RWF but that simply doesn't seem to be an option for the foreseeable future (regardless of how much top guilds competing in the RWF beg for it).