Work with me on this one, I think it could work, but not quite sure how to phrase it. If someone can help with the phrasing, then we get it to Jira and campaign for it. Let us get the wording and the balance right.
The problem is that cutting up land into 16m chunks has no consequence. The idea would work something like this:
"You are allowed a certain amount of land per tier level. That land can consist of your tier level land allotment / 256 number of parcels. You will pay an extra $1 U.S. in tier fees for every parcel over your allotment."
So if you are at 1024m in tier, you can have 4 parcels. If you cut it into 6 parcels, you must pay an extra $2 U.S. per month.
The actual amounts can be changed, it can also be grandfathered so it only kicks in for new parcels. This would mean everyone can have some small parcels, and larger land owners can have more distinct parcels, but ad farmers who have a large number of parcels but a relatively small amount of land will either be forced to sell or pay up.
I've watched new sims come online, and have seen that even before the first large parcel is sold often all roadside parcels are already cut up. Ad farmers have a negative impact way out of proportion for their numbers, one ad farmer can destroy the look of an entire sim.
The difficulty with proposals to stop them in have been in creating too many restrictions for those who have legit reasons for a few small parcels around their larger parcels. I think this proposal contains the essence of a working solution. If you like this idea, please help with the wording and the balance, then let's campaign. Ad farmers are the lowest scum in SL, they only care about the few pennies they get in ad views and are willing to destroy everyone else's enjoyment for that goal.