probably easier to track it by number of Move specific software sales I'd rekon, then run it through some ratio or formula when one becomes available to see the sales of Move per person than count every Move controller sold
400 000 copys of "x" sold should be a good indication that there are at least 400 000 move controllers out there.
however that will just get crazy because not every Move controller owner is going to buy every move enabled game so i dunno
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