IIRC though it's actually getting easier to make the best seller list over time. The reason for this is that before Amazon and computers, being on the best seller list meant getting your book on the table in front of the door and next to the cash register in all the bookstores. This is no longer the case, because most books are sold by a handful of chains, and they don't do their laydowns based on the best seller lists but rather based on computer algorithms and deals with publishers. In B&N making the best seller list still gets you a discount and onto a special shelf, but it's still less good than getting onto the front table.

Because of this the only people with a big incentive to game the list anymore are people who want to use the credential to use consulting, so there is a lot less competition than there used to be. Of course new authors still try to game the list all the time for ego, but usually they do it half-heartedly so if you really have a permission asset in place and a good strategy its not that hard.