Started by turning off adblocker, but not NoScript. Allowed everything except the obvious advertising domain “blogherads”, and no significant increase in usage.

Allowed that and it added a whole bunch of domains to the list, meaning that it polls all the other ad providers and tries to run their scripts. Tried enabling those a bit at a time and noticed nothing in particular. The ads did start taking up a small amount of extra memory but no runaway effect.

I didn’t get around to allowing them all, but I did notice that at one point I tried to scroll the page and it loaded ad section after ad section indefinitely as I scrolled.

If you have an extension that tries to load a page right to the bottom, then that would almost certainly cause a runaway effect. It would try to load an infinite number of ads below where you were viewing the page.