Wow... the U.S. government is like a greedy business... resembles a cable company whereby you have to pay crazy fee's to cancel a service. What a shame.
Not anymore. You're referring to an old rule. The HEART legislation, passed last July, changed that rule. Now, you no longer owe taxes after renunciation. Instead, a capital gains tax is levied against your worldwide assets as a condition of the United States releasing you from citizenship. So, they rob you once and you're done.
just to add...you will be taxed if you spend more than 60 (or is it 30 days?) in the country just like a citizen even after you've renounced and paid your cap gains tax. So, once you leave, you really have to leave.