When using HTTPS everywhere I frequently notice the ruleset counter next to the search bar. I understand the counter represents the number of rulesets for each page, which can be seen by clicking next to the number.
It makes sense for some pages to have many rulesets, as it it obvious that they are plugging into other locations to retrieve other media. However, on other websites, I am at a loss to understand why there could be more than a single ruleset. For example, on the BBC's website, I am getting two outside rulesets (one from Optimizely, and one from Google Services Simple). It is not clear from looking at the BBC homepage that any media is retrieved from elsewhere.
I haven't administered a website in some time, so maybe there are new things I don't know about. But shouldn't any rulesets which are being loaded be obviously due to a media retrieval (such as adverts)? Otherwise, I can't see what the ruleset is doing.