It doesn't take much too put a person living hand-to-mouth "into bankruptcy". The "Bronze plan" (cheapest) has a deductible of $5,000.
So any Bronze plan participant with less than that amount in the bank will be in default immediately if he has a $5,000 injury. Now if that person were saving his $250 per month premium (hypothetical) rather than flushing it down the Obamacare rathole, he could cover the bill in just 20 months.
Admittedly that doesn't solve the problem of the $100,000 illness or accident, but in that situation the careful student will note that Obamacare has no preexisting conditions. So if you get badly sick, you go down to the Obamacare office and get on the plan; pay the $5000 deductible and $3,000 in premium ($250 per month for a year). The taxpayer pays the rest ($95.000.). When you're well again, you get back off the plan. What a deal! The only way you will not play this game is if the government makes the penalty extremely high so that it is tantamount to "single payer healthcare".
Interestingly, SCOTUS has said that if the "tax" is large enough to change behavior, then it is unlawful. So just because they are getting away with a penalty "tax" of 1% of income, there will be lawsuits when goes to 2% in 2015. Their plan I think is to take it much higher. I don't think SCOTUS will allow that.