Xkcd

xkcd is a webcomic by former NASA roboticist Randall Munroe. It is one of the most popular webcomics today, and is an influential part of geek culture. The focus is on math, science, Internet culture, and personal relationships from the perspective of an introverted geek &mdash; the same perspective shared by most of the target audience.

Although far from confrontational, xkcd has occasionally dealt with controversial topics, and is firmly and consistently pro-science. #154, for instance (see below), takes the attitude that although the scientific consensus on evolution and the age of the Earth is correct, there is no reason to be bothered by others' willful ignorance, so long as they are not in a position to make terrible laws based on that ignorance. One comic criticizes homeopathy, another comic attacks global warming denialism, several mock conspiracy theorists, and another is strongly critical of pickup artists. Aside from these topics, the comic is notoriously neutral when it comes to religion and politics, in contrast with its more abrasive sibling SMBC, though it made an exception to endorse Hillary Clinton over an anthropomorphized fart in one comic, and skeptics have proven an acceptable target at least once. Comics have criticized several logical fallacies, some of which including appeal to moderation, the gambler's fallacy, and post hoc ergo propter hoc.

xkcd and the Internet
Munroe has a talent for putting relatively simple ideas in amusing and memorable joke strips; as such, xkcd is often quoted, linked to, and/or embedded in a post when there's a discussion on the Internet about science, math, personal relationships, or the Internet itself. Examples include the very common use of #285 (see below), using Wikipedia's tag as a way of criticizing someone else's unsupported assertions, as well as...

SIWOTI syndrome
SIWOTI syndrome is a strange psychological affliction affecting many Internet users — more likely an immune response than something viral. The abbreviation comes from "Someone is wrong on the Internet", a phrase used in #386 ("Duty Calls"). The syndrome manifests in persistent attempts at convincing people who are (definitely and indisputably) wrong that they are wrong. It is suspected that analogous to the role of in human aggression, the syndrome is the underlying reason for the existence of Internet flame wars, the organized skeptical movement, and this very wiki.

Joking aside, while it wasn't in the original strip, the phrase "SIWOTI syndrome" is often used, including by skeptics. We'll leave it to some other intrepid folklorist to determine which bright head(s) first came up with it.

Argumentum ad xkcd
Some cartoons are gross oversimplifications, outdated, or a combination of both. This is okay as it's an internet cartoon that primarily aims to amuse, but some cartoons get repeated ad nauseam as if to make a point.

The "goto" cartoon is an excellent example of the latter. The thing is part of a general "goto is harmful" misconception, propagated by people who've never really programmed in languages with goto statements and just heard that it's harmful somewhere. You cannot have a discussion on goto anywhere on the internet and not have this cartoon posted by a nitwit. Knowing Munroe, the comic was probably intended to mock the misconception.

The "correct horse battery staple" password cartoon is both a severe oversimplification and outdated, but still gets quoted often. The problem here is that entropy is only part of what makes a strong password. Password crackers can crack these passwords with a technique known as a "combinator attack", where a cracker will read words from a dictionary and combine them. Passwords such as "howdoyouthink!", "momof3gr8kids", and "ilovemySister31" can be cracked by this in very little time (when hashed but not salted) and security experts recommend against using it. You can still use the xkcd scheme, but you need to choose at least 6 incoherent words at random (the random bit is important and something many people get wrong) and should add some symbols and a number when required.

Gallery
Click to enlarge.