Spite-bidding has been going on as long as auctions themselves, and while it's petty and immature, it's technically "legal" in the auction world.
I don't think it occurs often enough to warrant anything other than case-by-case action, if any action needs to be taken at all. After all, it's an auction, and if someone really wants to buy every item on there, before anyone else gets a shot at it, that's pretty much the nature of the beast. They're paying their money, and receiving seeds or plants for it, and that's exactly how it's supposed to work. Even if they throw away the seeds, they still paid for them, and are free to do with them as they wish. In a grudge situation, chances are that the offending party will eventually tire of the head games.
I pay attention to the users who I'm bidding against for a different reason, so that I know who
not to bid against, either because they're persistent and competitive, wealthy, because they're overseas and taking advantage of the exchange rate, or, in the worst case, all three.
There are also users I tend not to bid against because they're friends. There are many strategies involved in the auction "game", all made possible because user names are not masked.
"Anonymizing" the bid process exposes the system to much worse problems, such as shilling, which is something I'm 99.9% happened to me once on the Lily Auction.
Shilling can take place via a second, "fake" L/A user name, or simply by having bids run up by a conspirator. Site management doesn't really have the time or means to detect it, so usually, the way it's noticed is if the "victim" figures it out. If bids were anonymous, it would be even more difficult to tell if it were happening.
