Recently on a number of websites, there has been a lot of discussion on whether academics should encourage the young to do PhDs. There has been a lack of real [aka non-temporary, well-paid] jobs for the recently qualified PhD-er in academia and as studying for a PhD is not well-paid, if paid at all, and it takes years, many people question the wisdom of pursuing this career path. Now, if you are doing a PhD because you want to be rich, or because you see academia as a easy career choice, then you probably shouldn't be doing a PhD in this market [if any]. And if you are doing a PhD and you are not enjoying your research [ok, the academic politics can suck, but I mean your own actual research- and I don't mean that you can't have bad days], then you shouldn't be there- because our love of the subject is why we do this. But, as someone who was paid to do her PhD, I really enjoyed the experience and I earned about as much as a full-time job in a supermarket. It was a lot of work, but I made my own hours, and I did something that made me happy. The loss in theoretical income that I would have earned in a graduate job was more than worth the experience.
Now, I was fortunate to get a job after the PhD, although it is contract work, so I am not suffering some of the angst of yet another year's miserable pay, multiple jobs, and scraping by, in the hope of hanging in there. And I understand that if you really want to be in academia, then having to hang-on in there isn't really a choice, but on the other hand, you wouldn't even have a shot at academia if you hadn't done the PhD. And, PhDs do not just qualify you to work in academia. There are a number of organisations that like researchers with PhDs, even those in the humanities, including the government- at local and national levels, and in the civil service; there are private organisations that do social research for the government and for private companies; the NHS employs researchers for health studies; there are also plenty of companies that just like to employ over-educated peoples. And, I know people who have got these jobs, so they're not imaginary. So your PhD is not worthless just because you don't work in academia, and indeed in the non-humanities, many people do PhDs with no intention of ever working in academia. The trick, and the angsty-bit, is knowing when to change paths.
Now, I know that there is the line of thought that if you need to go into a non-academic career than you have wasted time that could have been spent working up a career ladder. But, in this day and age [and annoying historical note, this seems to be true for a lot of history], few people remain in the same career for their entire lives and wider experience (such as a PhD) can translate into real financial benefits or advancement, just like other forms of life experience. People with PhDs have transferrable skills!!
So I guess my point is, if you want to do a PhD and you go in with eyes open knowing that there is no cushy guarantee of an academic post at the end, then do it. Life is more than money and, well, who wants a real job anyway?