Long-gone UK-based engineering magazines: was it something I said?

Between 1986 and 1999, I wrote for a dozen or more UK-based engineering magazines in one capacity or another. Many of them are now long gone, usually either closed, merged into others and quietly retired, or only maintained now on a website (remember "Engineering Materials and Design", "What's new in Design", or the UK's "Design Engineering" magazines?). Was it something I said?
Being sent out free, one of their main problems was the difficulty (and huge expense) of maintaining a good circulation. If you moved job, the chances are that the magazine would still be sent to your old desk, and might continue to be so for years, perhaps being read by someone else, perhaps being quietly binned. As time went on, the advertisers who funded these magazines developed their own up-to-date customer and prospect lists, and today many produce their own superb quality magazines. To take just one example, SKF's "Evolution" is published in print four times per year in eleven languages - show me an independent trade magazine which does that.
The reason I'm reflecting on this, as Engineeringtalk reaches its 250th issue, is that things are so different with electronic distribution. It's hard work to bring a publication like this to the attention of new readers (we might have a circulation of just under 50,000, but we've hardly scratched the surface of our potential worldwide readership). The difference compared to conventional magazine publishing, however, is the fluidity of that readership. People often assume that once we've got you as a reader, we hang on to you tenaciously. Far from it. We publish a one-click "unsubscribe" link at the top (yes, the *top*) of each issue, and we honour that. In addition, when people leave a job (or their email address becomes redundant), our issues "bounce back" and (unlike postal distribution) we know, instantly, and can remove that name. Last week, for example, 450 people joined our circulation and 200 left. That happens every week. And it's a good thing.
The result is that an incredibly high proportion of these newsletters get read, and I'm well aware that we're now producing information for a massively larger audience than was ever the case on the magazines where I began. Fortunately, the business model seems quite sound, and I look forward to still being here for a 500th edition.