If the club is so packed that capping membership is on the table, why not invest in more infrastructure to handle the greater number of users, assuming the land is available to do so? If the current facilities are being used to their capacity, it is time to upgrade the facilities... Put in more skeet fields, more trap fields, expand the rifle/pistol range, broaden the sporting clays course/5-stand, make sure the club is open for shooting more days a week, ect.
Turning away people with cash in hand is just plain dumb, especially in this economy. And unless you're the only game in town, they're going to the club down the road to spend their $...
One club I'm a member at capped it's membership @ 750 when they installed a new 200 yard rifle range, to make sure they wouldn't get overwhelmed. They never did, and incrementally raised the cap as time went on, and eventually dropped it all together when it was realized it was hurting them WAY more than it was helping. The only benefit was that it encouraged members to renew on time, if they didn't pay on time their membership lapsed and they had to go to the back of the waiting list and start from scratch. In the mean time, we lost a lot of good members because of this (they weren't willing to wait until their name came back up, and joined other clubs instead), and turned away at least 20-30k in profit from memberships... It seemed like a good idea @ the time, since the huge influx of new members was a complete unknown, but unless you expect a huge influx of members like we did, I see absolutely no reason for one.