This seems a common issue: a user decides to try out Adblock Plus, goes to the context menu and clicks "Block Images from bla-bla.com". He never noticed this menu item before, so this must be from Adblock Plus. And then he fails to recognize how he can unblock the images again - Adblock Plus isn't showing any filters. So he uninstalls Adblock Plus and keeps complaining about how bad this extension is - his images still don't show up.
There is a suggestion in Bugzilla about integrating Adblock Plus with "Block Images from" somehow. The functionality of the two is very different however, and Adblock Plus makes the built-in blocker redundant. I get the impression that best thing that we can do here is to remove this item from the context menu alltogether. There would be a hidden option (about:config) to switch this off.
I am considering this change for Adblock Plus 0.7.0.1, to be released this weekend. Any objections?