I don't really see the problem with this, now hear me out.
1. This is not Facebook charging for all groups, or even Facebook determining which groups do charge. Rather they are giving the option for group admins, which for the most part are private individuals, to charge admission to the group that they run.
2. To my knowledge there is no way for current group admins to make money directly for all the work they do in their group. Right now they are forced to use referal links to stores or otherwise direct readers to outside websites where the admin makes money off the ads. These methods don't work for all groups.
3. That leaves two real options for Facebook in tryting to compensate group admins and continue to build robust groups. Either, Facebook gives admins a share of the ad revenue they are making from the pages of the group, or they build another revenue stream for the group.
4. I actually wouldn't even be too upset if facebook took a small percentage of the charge, 10%. This would give Facebook another none ad revenue stream. Perhaps they could take 5% for regular groups and 10% would allow for an "ad free" group. To me that would make facebook groups an attractive option for my private group.

Just my 2 c.

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Step 4. Profit !

Can someone post the test here. I think it would be really interesting to see what percent of Slashdot readers can pass the test.