It's important to strike a balance. Obviously you want to attract new members, but ideally you want those members to post regularly at the forum, and not just play in the freerolls!
Unfortunately whenever you introduce a post count requirement you will find some people that will just spam their way to the required post count, then never post at the forum again, which creates lots of work for the moderators that have to clean up the resulting mess.
So you need to find a balance that works...
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"You shouldn't let the strength of your hand affect the size of your raise. A tough poker game is like real estate.
The three most important factors in deciding how much to raise are: Location, location, location."
Chris Ferguson