great, and a suggestion Rated 5 out of 5 stars
a great add-on, thumbs up, and here's a suggestion: why not add a function wherein you can block *everything* on the web except for 1 or 2 stated sites. So instead of identifying the sites you wish to block, identify the sites you wish to allow...This review is for a previous version of the add-on (0.6.3.1-signed).
Thanks for the review! Actually, the functionality you mention is already there: just use wildcards (* or **) and exceptions (+). See the LeechBlock examples page for more details.