Also, by using DuckDuckGo [1] over HTTPS you get the same ruleset in HTTPS Everywhere [2] even if you don't have the extension installed.
[2] http://www.gabrielweinberg.com/blog/2010/09/duckduckgo-imple...
Pages include resources from https-everywhere'd domains and for whatever reason (mostly that the ssl versions of those resource urls aren't serving the same resources, or have broken certs) those resources fail to load. Within an hour of using it I'd seen it break 3 or 4 sites, so it got disabled.
You can manually disable it for individual sites, if you recognize that it's the problem, but if some minor resource fails to load it might not be obvious.