I'm a postdoctoral fellow - which means that I have my PhD, but no permanent job; I'm spending a few years doing research in a lab run by a more senior scientist. This is a typical part of the career path for most people in the natural sciences who want to direct their own labs at a research university or with a company.
While a postdoc position offers valuable training, its also an excuse for institutions to get work from trained scientists without paying them very much. After getting your PhD (generally 9+ years of training, if you count college), you can land a postdoc position with the lucrative starting salary of $36,996, which really, really makes you feel like that PhD was worthwhile!
But besides the salary, you get screwed by the IRS because according to the IRS:
1. You're not an employee - not of the university you're at, nor of the government organization funding your research and salary. Thus you technically have no employer-sponsored health insurance; all of your health insurance premiums are taxable income.
2. You're not self-employed either, by the standards of the IRS - which also makes you lose out on certain tax benefits.
3. You don't actually "earn" any income - by the standards of the IRS, what you are paid is a living stipend, not wages paid for a service - so in my case, with 3 kids, I get screwed on certain child tax benefits - such as the ability to deduct any daycare expenses.
4. You are not a student - postdocs already have all the degrees they want; they're generally not looking for more. But not being a student also screws you in some instances with the IRS. In the US, we're supposedly worried about the fact that we're not training enough scientists to fill our society's future needs, but unless you really, really like science, there is absolutely no incentive to choose it as a career.
So how do we get college kids to sign up? Easy: don't tell your freshman biology students that after 4 years of college they'll need another 5-6 years of grad school, and 3-4 more years as a postdoc before they land their first permanent job and get to do the things their friends in other professions are already doing, like saving for a house, retirement, kids' college, not to mention vacations.
Oh, and we also shouldn't mention that because of flat NIH budgets for the last few years, its harder than ever to get money to do your research.