If you want to make these contests fair .... Forget about the post count altogether.
A member that enters a certain giveaway contest gets one chance to win ... This ECF member's name stays in the contest for a chance to win as long as the contest is still going on ... Once the member wins, his name is pulled out of the randomizer .... Simple.
Why should we give someone that posts a simple "Good Morning" and a simple "Good Evening" and makes frivolous other one-sentence posts 50 times a day a better chance of winning than some guy that has a real job and can't sit at his computer 24 hours a day making worthless one-liner posts or posting silly photos to the contest
thread on a day-to-day basis.
It's the only fair way to run a giveaway contest in my opinion .... Everyone that enters has an EQUAL chance of winning.