The answer is simple and been done before. Revert all the karma to the date prior to the karma store opening. That happened before when a couple of clowns found the glitch in the karma store and created millions of fictitious karma into the system.
Everyone was reverted back to that point. That should happen again and is fair.
The people who paid for karma through the store should get that amount added to their totals b/c that's a legitimate transaction (that karma would be worth more at the new levels as well).
Then either:
Limit the amount of hits per day for a member
Set a max karma hitting number to say, 200 (this would end karma inflation cold alone)
Or set a daily maximum alotment of karma to be spent, say 5000 points or some arbitrary number that can be spent in karma.
Mistakes were made in the implementation of the karma system and right now the system is just broken. Just revert us back to that previous time we were kicked back to, people were bitching at us for the karma store heist and losing karma so its nothing new. Just identify the areas that have caused the system to be broke since that day and implement changes that you have identified as contributing to the karma inflation.
Whether being only to hit so much k with a post, limit the amount k hits that have karma, max alotment of karma to be spent etc...
With 30 hits per day and karma whoring networks, growth will become exponential making the karma system even more ridiculous than it is now.
So if we ever get karma poker, it wont be fun if heavyhitters have that much karma.