Thats the problem with running promo like this,Free 500 doges just for sign up,i think almost every one sign up just to earn these 500 Doge coins.
I think there should be some mobile verfication and only verified users should get 500 Doge coins and not other ones.
Yes righly said,every one love freebies,so even getting a small amount of dogecoins,every one would take it.Specially newbie who are new to earning crypto-currency,they use VPS to just make multiple accounts,take the bonus and withdraw them and then no use of that account.