Obamacare Tax Penalty, collectible?

Odd but true, Obamacare's tax will not be collectible by the IRS in all situations:  Strangely, the IRS can’t collect this tax without the taxpayer’s help.  If the taxpayer doesn’t fork it over voluntarily, or have a refund against which to apply it, the IRS can’t use its usual collection tools — levies, seizures and so on —  to collect it.  That means a lot of people will make sure to fiddle their W-4s  so they never have an overpayment on their 1040s.