Purges are the destruction of existing data on the wiki. They are similar to cuts in terms of general motivation- the excised data that is purged is deemed irrelevant, a waste of bandwidth, and simply not a useful page to begin with. The difference is that cuts are actions taken on specific pages that have been identified by members of the wider community as being worthless pages- Cut Masters are informally expected not to make any cut proposals on their own. Purges, by contrast, involve the destruction of wide swaths of wiki data owing to the kind of general data they are.
I first became aware of the idea of purges in the Trope Renames portion of my tenure at TV Tropes. While it's possible that there were purges before my time, this is unlikely- the wiki simply wasn't large enough to warrant purges. Of course, depending on your point of view, the Great Crash could have been the wiki's first purge, as it summarily destroyed nearly all of the wiki's content, albeit by accident.
Defining purges makes them sound a great deal more sinister than they really were. Initially they were just summary executions of old, archived data in the forums. Aside from the few technical forums most of the posts were quite useless to overall operations- the forumites who frequented the various Media forums, Yack Fest, It Just Bugs Me and the like were just having fun. It was fairly reasonable to assume that nobody would much care about forum threads that were over a year old. Bear in mind that as the wiki forum software at this point did not have search capabilities, old threads were nearly impossible to find anyway unless one can remember the exact date in which the last post was posted.
For the purposes of this blog, purges are mainly important to illustrate what I mean about TV Trope's nebulous, untold history. Topics in forums like Trope Renames and Wiki Talk were not exempted from the forum purges simply because these forums dealt with page maintenance. They, too, were eliminated from the wiki. Because of this there's a great deal of discussions leading to major page action which a lot of people simply don't remember and can't be verified independently.
I'd like to iterate here that I don't think the purging of this material was done with malicious intent, and that had anyone any idea the importance Trope Renames discussion would have on the website's remembered history, things likely would have been handled differently. While the forum is the most obvious place to purge data from, YKTTW archives also go through this process. YKTTW discussions, unlike forum threads at the time, directly linked to launched pages be they original lead-ups to trope creations or discussions that foster renames. As a result, much of the Trope Rename action that took place during the YKTTW process of renames can actually be verified, though rename proposals were not launched in a uniform manner and regardless of how many times a page has been discussed in YKTTW, generally only one YKTTW archive link appears on the discussion page.
Of course, however I dress it up, the fact of the matter is that a lot of information does not exist anymore, and realizing this was a major motivation for me to start this blog. In this manner being banned from the web site is not so great an impediment to recounting its history as one would think- in many of the most interesting cases I would have to be working from my own memory anyway.
To the best of my knowledge the practice of purging has never been questioned, mainly for the reasons listed above- what's the point of archiving data that the wiki simply has no use for? This was, in fact, my personal opinion of the matter when I first heard of the existence of purges. Their existence was worth taking note of for future reference. Then, we move on and get back to work. Given the chronic difficulties the Trope Renames forum had in trying to attract new members, we all pretty much assumed that nobody was much interested in the decision-making processes we used in the first place.