Came across this report yesterday. Turns out AdBlock Plus (ABP) increases memory usage due to the way it works. Check out this post by a Mozilla developer for more info. The latter post also includes responses from the ABP developer.
I disabled ABP on my browsers. Not because of these reports, but because I had been thinking of disabling it for a while but never got around to it. (I know it’s just a right click and disable away, but I never got around to it! :) Mainly coz I use the excellent Ghostery and Privacy Badger extensions, and these block most of the trackers and widgets I am interested in blocking, so I have never used ABP much. I had installed it a long time ago and it gets installed automatically on all my new Chrome/ Firefox installs thanks to sync, but I never configure or bother with it (except to whitelist a site if I feel ABP could be causing issues with it). Yesterday’s report seemed to be a good excuse to finally remove it.
This Hacker News post is also worth a read. There are some alternatives like µBlock (seems to be Chrome only) (github link). It is based on HTTP Switchboard and is by the same developer. I have used HTTP Switchboard briefly in the past. Came across it as I was looking for a NoScript equivalent for Chrome and this was recommended. I didn’t use it much though as there was too much configuring and white-listing to do. (For that matter I stopped using NoScript too. It’s still installed but disabled except for its XSS features). Like I said, my favorites now are Ghostery and Privacy Badger – the latter is especially smart in that automatically starts blocking websites based on your browsing patterns (in fact Privacy Badger is based on ABP).