You publish a major daily newspaper or magazine. You want to have your cake and eat it too (charge for web access and sell online ads).
Instead of forcing readers to subscribe to an electronic edition, just ask them to enter an access code from a recent print edition of the news paper. The access code is one of those warped text and numeric images that websites use to thwart bots. So if you subscribe to the paper or at least buy a print copy every now and then, you can access the web archives when you need to.
Simple, easy enough to implement, and this has the added bonus of encouraging people to buy the print edition. I am a case in point, I read the NY Times pretty much every day. So I am already paying several hundred dollars per year. I don’t want to pay twice to read articles I could have read in print. Plus I’d like to be able to read the edition anonymously, something the disposable access code trick would allow.
Of course, this is not a perfect system, people can post access codes online easily enough, but on balance there are enough honest people to support a system like this, enough that maybe this is worth a try….