Many political figures opposed to the ACA have made a big point of complaining that the delay of employer sanctions and the lack of enforcement mechanisms will make it easy for individuals to cheat the system and take advantage of the subsidies in the health care exchanges. This was a big complaint previously made by speaker Boehner and repeated today by Michael Gerson. It's worth noting what this cheating would mean and the incentives provided to workers.
The deal is supposed to be that workers are eligible to join the exchanges and get income based subsidies, if their employer does not offer them an affordable (based on their income) insurance policy at work. Because the government is not prepared to enforce the employer sanctions for not insuring workers and does not have data on the nature of the insurance offered to workers entering the exchanges, there could be some workers who enter the exchanges and get subsidies who actually are offered affordable insurance from their employer.
The issue here is how many people do we think will fall into this boat. To take an extreme example, suppose a worker has an employer that pays the full premium for their insurance. What incentive would this worker have to lie their way into the exchange so that they could get a plan that is subsidized by the government?
If the worker is in a low-income household then the subsidy could be close to 100 percent. In this case, if the insurance offered through the exchange is better than what the employer offers (do opponents of the ACA think this will often be true?) then the worker would have an incentive to lie their way into the exchange, but otherwise they would be better off taking the deal from their employer.
Of course most employers do not pay 100 percent of the premium, but the cases where workers are likely to get a better deal through the exchanges than what they would get from an employer who offers a plan that fits the ACA definition of affordable are likely to be relatively limited. Therefore the idea that there will be massive cheating by this measure seems unlikely.
By contrast, if ACA opponents are actually worried about the government being ripped off, there are many small business owners who list personal expenses, such as a car purchased primarily for personal use, as business expenses. They list these items as business expenses, thereby having taxpayers pick up the tab.
The money lost to the government through this tax dodge is almost certainly at least an order of magnitude greater than the money that could potentially be lost through improper subsidies. (For the math here, if a business owner is in the 39.6 percent tax bracket and buys a $30,000 car, this will cost taxpayers almost $12,000.) Anyhow, if opponents of the ACA are generally concerned about the government being ripped off, they might focus their attention on improper reporting by small business owners. There is a lot more money here than in improper ACA subsidies.