Whee. There's now an Adblock extension for Epiphany. Simply takes a list of patterns (* and ? recognized, with g_pattern_match()) in a single text file, and prevents Mozilla from ever downloading the files. Works splendidly.
Possible enhancements: FAM monitoring of the file, to update blocks on-the-fly; a UI to edit blocks (I'm tempted to just make it open the text file); regular expressions support from libegg; UI enhancements ("block ads from [host]..." on right-click)...
However, as useful as Firefox's AdBlock extension is, it's a perfect example of utter bloatware. I don't want to go down that path; so besides FAM, I'm not sure if I want to put anything else in.
But I ought to port it back to Epiphany 1.4, so I can actually use it before another 6 months go by.