They also could get together with a whole bunch of friends and plan ahead. You allowed to spam the link that's not the problem, spamming wont get people to click it so spam if you want . What will help however is if a player has some friends or contacts they can send the link to right away then have people on websites know before hand well in advanced to click the link and have everything pre planned, this is fine to but the problem is when they preplan all their friend to submit their link to traffic exchange or even to a Facebook group that swap clicks. So that wouldn't be so fair.