On a related note, what do you think of the Magic structure, where various cards/sets are banned from certain formats? (I don't mean for Dominion, but for Magic in its own right.)
For individual cards in tournament formats, they obv. need to ban the minimum number to have tournaments not suck, and they try to, and the minimum number is not always zero. As they say, they have to take risks to have exciting cards, and that means sometimes they'll blow it.
For sets rotating, there are different perspectives.
- For Wizards of the Coast, it makes a lot of sense to rotate what sets are legal; it propels the cash cow.
- For tournaments, it's good because otherwise you solve the formats.
- For home play, you can just ignore it all and should, and make an endless series of themed cubes.