Depends on the audience-acronym pair. I don't think HTTP needs an introduction in a technical article, OTOH (on the other hand ;) ) a general newspaper should probably expand HTTP but not WWW.

Perhaps a stroll through your own comment history (or the comments of any other HN (hacker news) user) would illuminate a lot of places where acronyms are used without introductions. TBH (to be honest) though, I'm not sure if every one of those should always have one or sometimes not.

As English speakers we often take for granted acronyms such as DB or even USA. For foreigners these can also be inscrutable.