Dealing with the Gil Sellers
Several ways square could handle this, the current way is banning accounts/characters. In all honesty that kind of works but as we have all seen the seller just deletes that account and creates another one at very little cost, a month in the game is what 12.99 for entry or 14.99 for standard for the first month. Also was hearing about a special on steam for a while something like $5 for a 30 day subscription. Either way it really isn't costing the gil sellers any major income to delete and create another account or character. Especially if the banning seems to only happen once a month. So for 14.99 they can create a character on 40 worlds. From this stand point square is loosing the battle. Even if they ban 1000 accounts a month that isn't deterring the gil sellers from creating another account.
A few other methods would be to reduce the number of worlds that you can create characters on to say 3. I mean honestly how many real players need 40 characters on 40 different worlds? Most really players have at most 3 to 5 characters max, usually or 3 on a world. So you could say 3 characters max per world rather then 8, and say 5 separate worlds max. So for a total max of say 15 characters. Being that when you ban an account you ban all characters associated to that account. It isn't profitable to have multiple characters on the same server for the gil seller. Its more productive from an advertisement stand point to have multiple accounts on multiple worlds. By limiting the number of worlds an account could have. It will limit the number of gil sellers because it would be more of an investment on their part. Also it would generate more revenue for Square.
Another method that could be changed to the banning process. Would be rather then ban accounts, ban activation keys. So not only would the gil seller have to invest in the 14.99 per account per month. They would have to invest 29.99 for another activation code. This may impact number of codes for players but I believe that the 3.8797312*10^27 codes that are potentially available with the current registration code system yes thats 3,879,731,200,000,000,000,000,000,000 registration codes that could be potentially available at one time. The banning of registration codes shouldn't have an impact on player sales. Not to mention at $29.99 USD thats roughly around $1.16353138688*10^29 so big time potential money maker for Square.
Only other way to remove gil sellers is so some how set up the coding to prevent 3rd party bots but then again that has been a fight since the beginning of online gaming.