Being unable to afford health insurance means two things: first, not having regular doctor visits where both minor and potentially-lifethreatening medical problems could be detected early enough to effectively treat; and second, needing to be very, very rigid in what one considers an 'emergency.'
In this category, there are those who do not receive any health benefits from their jobs, as well as many of us who are self-employed. Many in these two categories simply cannot afford the high monthly premiums for health insurance. I have heard and read a variety of viewpoints, all with the notion that everybody can afford health insurance-- get a different job, go into a different line of work entirely, cut back on all of your other expenses, etc. etc.
For me, personally, the only legitimate option is to join a union which includes significant discounts on health insurance. While joining a union is not inexpensive either, most people who cannot afford health insurance do not even have this option. Obama's platform about "affordable healthcare for all Americans" has clearly missed the mark.