Hm… I’m not sure if this is enough to defeat the strategy.
It looks like even with that service, you have to sign up for Form 1583.
Even if they’re willing in incur the cost, there’s a real paper trail pointing back to a real person or organization. In other words, the bot operator can be identified.
As you note, this is yet another additional cost. So, you’d have say … $2-3 for the card + an address for the account. If you require every unique address to have no more than 1 account … that’s $13 per bot plus a paper trail to set everything up.
That certainly wouldn’t stop every bot out there … but the chances of a large scale bot farms operating seem like they would be significantly deterred, no?