Meh, people said the same thing about Chrome but I know of almost no one who thinks that has been bad either for the market or any individual segment of the market.
If previous versions of Adblock are still the base code for the new versions, it doesn't block the ad. It merely hides it. The ad is still loaded, you just don't see it. This limitation is/was because Chrome didn't allow extensions to have the access they would need to actually keep an ad from loading.
I haven't used Chrome with AdBlock in maybe a year or two, so this might be out of date. But that's what it used to be like, and that's where the perception is coming from.
I wish this meme would die. There's a kernel of truth, that initially Chrome didn't support blocking network requests, but that's because of the tradeoff of extension compatibility vs power that Chrome made. Firefox addons (as originally designed at least, I'm not up on their latest efforts) have always been incredibly powerful, but that power comes from calling internal browser APIs that might change from version to version.
Chrome extension apis have to be explicitly designed and developed, and backcompat is taken care of, so your extensions don't all break every six weeks when Chrome updates.
Sounds like a load of FUD to me. DOM elements are DOM elements, aren't they? How would Chrome's JS interpreter be able to discriminate ad content from anything else?
If you want to investigate how it works, open the extensions tab and enable developer mode. You can open 'background.html' for Adblock and check out what it does.
