Basically it boils down to OUTbound order volume. The more you send the higher your rank.
There are some other factors as well, that "might" be taken into consideration, like MarketPlace purchases, Credit Card Clearings, filling for dot.coN and so on.
I tried on a couple different occassions to get FTD to modify their "qualifications" thinking that a shop, no matter the size that sends 100% FTD, buys the products, and uses the programs, deserves more consideration tahn one that only sends, kind of in the concept of "Being FTD". However thats never been the case.
Just like, Krogers is always at Top Member functions based on their 2500 or so stores...
I even tried once to get them to do a Top Member Event for the TOP !)) FILLERS... but since there is no money in it for them, they see no advantage to such a party, but I think it is only fair.