The same suggestion has been made as a alternative if "mandates" are found unconstitutional - purchase of health care via the exchanges (which are a market mechanism, and would likely be attractive to many economic conservatives if they had not been part of a Democratic proposal) would instead be made voluntary.
The problem is that to make any such system work, you need to deny care to those who voluntarily chose not to insure, otherwise the rest of us just and up paying (one way or another)for their care he they turn up at ER or public or charity clinics.
Since we are not going deny such care (at least to a much greater extent than we already "ration" care by income and insurance status), all such schemes encourage freeloading.
For this perspective if does not make much difference if you offer people "heath care stamps" eligible for the purchase of individual health insurance or offer people the opportunity to purchase subsidized insurance via exchanges (except that their pooled purchasing power will likely be greater via an exchange), as long as such purchase is voluntary before need, and care is available to non-purchasers, there will be a strong incentive to avail yourself of free care "at need" rather than "pre-pay" via the purchase of insurance.
This side of the equation does not get much attention: lots of people are thinking "OMG, I will be forced to buy insurance", while ignoring the fact that those of us paying taxes are already "insuring' those who will not insure themselves.
Threatening them with $250,000 fines ain't gonna' work either.
What your asking for is some spontaneous organizing on the part of the target population ~ and I doubt you'll care for the results. Now it's not going to hurt me ~ I'm ready with the armbands to sell them, and all that. $2.00 a head should make me quite wealthy.