they still need to have multiple device to get the reward.
Actually, this is not true. You can create a wallet, do the airdrop, backup the seed, blow away the wallet, (if on PC you got to delete folder aftering doing the uninstall, on mobile you just delete and reinstall app) and reinstall the app and do the next one.
Possible but could be detected, again, the device information cannot be change, even they delete the folder the device information will still be the same as the first one. and I know byteball team is fighting the every possible abuse.
Not "possible", it's a fact. I registered both of my main accounts and I know others have done tons. Detected? Doesn't matter, abusers will dump the funds onto Bittrex almost immediately. Even if they lost the smart contract funds, they still make out big.
You are correct!
You are absolutely right. To think that this behavior was completely unexpected by Byteball is a bit naive, really. As I wrote in a comment to the article, we just might have put quite a bit more thought behind this than people gives Byteball credit for.
If you delete your wallet, the steembot gets rebooted with the new wallet on the same device and you can attest with a different account. I don't think you can keep your smartcontract rewards unless you go back and restore all the wallets in a year. There is no way of dumping private keys from the wallets.