"there's an incentive for readers to withhold more valuable information to others (instead of spreading them and making money with Google Adwords)"
There are two problems. The first one is that you make an assumption here, that individuals choose what's in the best interest of the group (if it's only about the individual, the Adwords money might outweigh the information value...). Secondly, even if the assumption holds and people will behave according to this rationale, then still it takes only two or three odd, less-rational individuals to redistribute the information, thereby devaluating it back to free.
That doesn't mean your model won't work. It seems it will (and does already) work very well for something like The Economist - perhaps it simply requires a certain type of readership...
First, I assume self-interest, not group-interest. That's what the club is for: The more people become members, the more content anyone gets, including you as a member. This is guaranteed by the club structure. For additional effect, the club may also own the copyright of the content.
Second, redistributing information is work. You can't simply copy'n'paste articles due of copyright. Even if this still pays for some individuals, finding good information is also work. It's easier to become a club member, especially when you have additional benefits such as being the first to know by automatic notifications, being able to set manual filters by following, being able to get to know other members by following, etc.
There are two problems. The first one is that you make an assumption here, that individuals choose what's in the best interest of the group (if it's only about the individual, the Adwords money might outweigh the information value...). Secondly, even if the assumption holds and people will behave according to this rationale, then still it takes only two or three odd, less-rational individuals to redistribute the information, thereby devaluating it back to free.
That doesn't mean your model won't work. It seems it will (and does already) work very well for something like The Economist - perhaps it simply requires a certain type of readership...