As a general rule, I am not a big fan of writing for free. I wouldn't ask my doctor to work for free. I wouldn't ask the person who collects my garbage to work for free. I rather think that people who are offering "exposure" and not cash are running a scam. Perhaps a legal scam, but a scam nonetheless.
And yet you see this sort of opportunity offered in many different places. As in: "While we can't pay you, we do offer you exposure that might result in..." This has only increased as the Internet has increased.
I do understand that many of these publications have little cash with which to pay writers. Fine, if you don't have money, write it yourself. That sort of exposure for writers is not really exposure. Exposure is being published in something that someone actually reads. Obscure websites are rarely that.
Now, there are a very limited number of sites where you write because you are part of that community. Science fiction fans have built up some nice sites along those lines. Yeah. This isn't that. I understand why someone might do that and enjoy it.
I am talking about sites that are clearly commercial endeavors, but which refuse to pay for commercial work.
However, there are very limited places where I will occasionally right for free. All of these places have significant website traffic that gets folks to come to my websites. Two of them are here and here. Notice, though, that these are sites where I went, signed up, and wrote articles that point toward me.I get traffic and share in the Adsense. These are not some faceless email that promised me riches through lots of exposure.
Some time back, I wrote a couple of articles for a website that is very large in my field. I did that for free. These articles include links to my online high schools website. These links result in noticeable and significant traffic each month. Also and importantly, I can trace those links to actual money earned through Google Adsense.
To recap, writing for free with the idea that it helps your bottom line almost immediately? Good.
Writing for free for exposure? Bad.