Well, I think it also might have something to do with 'cross-server' sales. IE someone buys a lot of stuff on their old server, and then sells it on their new server to 'launder' their gil basically. (since you can only take so much gil w/ you on a transfer). I *think* any items you carry over from the old server lose their crafter tags. Also, some items are drops (even HQ's) from leves etc. I don't pay too much attention to who crafted my purchases though so maybe I've just not noticed an influx of 'blanks'.