I'm not happy about what's happening here, but not surprised either. In fact the only surprise is it's taken this long for them to pull the plug. In retrospect a hint of the timing was at last November's SEMA, The Source Interlink booth was smaller and the stacks of "freebie" magazines were nowhere in site.

While we think as subscribers/readers, they think as advertisers first, content provision is just the vehicle. Businesses have been following the "most eyes" model for decades and took a shotgun approach to advertising. They'd place ads wherever they thought they'd get the most likely interested viewers. In the internet age it's become much more "scientific". A potential advertiser can track interest, and information collectors like Google, Amazon, et al can provide specific interest data that permits more targeted advertising presentations. So let's say you saw some commentary on here about a specific brand of electronic fuel injection. You Google or Bing the product name to get more info. Next thing you know, little pop up ads start showing up on your frequently visited sites and .............TADAH!, they just happen to be ads for the specific or similar product to the one you recently researched. Now that's targeted marketing. As a business person you feel that your precious advertising dollars are better spent on folks who at least demonstrated some level of interest in your product or service, rather than running an ad in some rag that broadly appeals to the market slice you HOPE will be interested in what you offer.
It's good business sense, and more productive for the business in question, plus helps them stay alive longer. In the end the survival of their business trumps the survival of the hobbyist magazine. A variation of Schumpeter's creative destruction.