I drove to Chicago yesterday. I-90 splits to local and express lanes once you are in the city. Ideally, you stay in the express lanes until the next opening back to the local lanes is the one before your exit. For that to work, you need to know when the lanes re-merge. The signs helpfully explain that the next exit from the express lanes is at Pershing Road. Great. Is Pershing before or after my exit? What number is the Pershing exit? This sign is a helpful reminder for people who already know where they are going, but not if you are just coming into Chicago and do not know what order the roads are in.
Our friends at Language Log define “nerdview” as “writing in technical terms from the perspective of the technician or engineer rather than from a standpoint that would seem useful to the customer or reader.” This is probably their best example, while our friends at Popehat present this gem that looks incomprehensible, becomes clearer through the comments, and then becomes fully comprehensible but completely useless after an informed commenter explains that the somewhat-reasonable explanation is not the true one (assuming he did not make that up).
In gaming, we might call this newbie-(un)friendliness. This has been a theme in the recent Guild Wars posts, both about the game and the community: the explanations of what to do assume that you know what you are doing. The developer or experienced player may have great difficulty dialing his knowledge back to the newbie, and then there are tiers of newbie because some people are completely new to the genre and some have experience with similar games, and then the experienced players need to unlearn what they have learned elsewhere.
Some games and communities do this intentionally. Developers usually would prefer more customers, but some like to keep their community small. Some players just don’t like to bother with newbies and want to keep casuals, trolls, etc. out. It is a form of initiation or hazing: if you are not willing to put up with X, we do not want you here. The original A Tale in the Desert was an accidental example (great community, strongly self-selecting), and I don’t know if Dwarf Fortress is intentionally that hard to get started on. Rogue-likes tend to like to have a painful introduction. Or, as was said about D&D as it left 2nd Edition, “THAC0 kept the riff-raff out.”