The ACA Penalties Are Not Just Toothless But Gummy
Abby McCloskey and Tom Miller write in the WSJ:

Those not exempt face modest fines compared with the out-of-pocket cost of paying premiums for ObamaCare-required insurance. For example, the maximum penalties for a single adult remaining uninsured throughout all of 2014 would amount to the higher of $95 or 1% of household income above the federal income tax filing threshold. This is a fraction of the cost of health insurance for potential enrollees in government exchanges.

The threat behind the penalties is even less believable. The Affordable Care Act explicitly prohibits the Internal Revenue Service from using its most powerful enforcement tools like criminal penalties and levying property--such as wage garnishment.

If the IRS manages to discover someone without required coverage for all or part of a year, it can do little more than collect the penalty by taking it out of any other income tax refunds owed to an uninsured taxpayer. That risk can be limited or avoided by reducing the amounts withheld from one's regular paycheck for income taxes.

For the mandate to have teeth, the size of the penalty would need to be greatly increased, exemptions would need to decrease, and enforcement would need to be stronger. Good luck with convincing congressional Democrats facing midterm elections to commit political suicide.

Even then, a tougher mandate still might not work. The CBO concedes that there is "little empirical evidence concerning individual people's responsiveness to health insurance mandates." In other countries with much higher penalties, such as Switzerland or the Netherlands, health-insurance mandates have had little success in changing the behavior of the uninsured and largely reinforced existing levels of coverage.