This is the sad state of online journalism. Publishers are realizing that they get a better return on investment from lots of cheap and mediocre content than they do from a smaller amount of high-quality pieces (see also: Journatic and Demand Media).
But as an aspiring writer, accepting these sorts of terms is the worst thing that you can do for the industry. You do this job so that you can put it on your resume and hope that someone else will hire you, but
who is going to hire you at a good rate? Prefix mag is doing over
2.5 million pageviews a month, and they're barely paying so you can imagine that there are extremely few well-paying opportunities for writers. A puplication is not going to pay a qualified writer a decent rate when they can get some college kid to do the same work for free or cheap. People have to band together and reject these sorts of shitty terms, it's the only way that Prefix or anyone else will pay up. Writing for pennies is the equivalent of crossing a picket line -- you're fucking over everyone else who's trying to make a good living for you own minimal gain.