An Archivist knows that many times valuable information is lost simply because it's only available online (for example in online newspapers) and the information is only available for a while (ususally years) because many newspapers don't keep all their archives and they are regularly deleting old articles. Many times such information can also be found in the printed edition of the newspapers, but searching into printed archives is so much time consuming, that, except for extremely important data, nobody will have the time to search for it. Therefore we can safely say that, most of the time, once the information doesn't exist online anymore, it is lost forever.
Therefore the archivist's priorities are:
- use the data in Wikipedia articles while the references are still available
- create backup copies of the references, using Archive.org, WebCite, or other archiving web sites.
- if the archivist doesn't have the time to add a specific information into a Wikipedia article, they will signal that information and it's reference in the talk page or in a resource page of the corresponding Wikipedia article, letting the other editors know about that information.
An archivist that finds a lot of useful information doesn't always have the time to add it all in Wikipedia articles. Therefore sometimes they will store the information and it's reference(s) in resource pages. Later, other Wikipedia editors (archivists or not) will use that information in the Wikipedia article. If the talk page of an article is not used much, the archivist will use it to signal such information (using it as a draft page or as a resource page).
Archivists are useful because they help other Wikipedia editors to develop the articles by supplying them new information for the Wikipedia articles and because they make sure the information is not lost, signaling it before it disappears.
Archivists are not in opposition to inclusionists, but they are complementary to them. Archivists are focusing on adding only referenced data. Also they are not exclusionists. Their focus is not to remove un-referenced data, but to make referenced data available, by adding it into Wikipedia articles, or at least storing it for later use by adding it into the talk pages of Wikipedia articles.
An archivist knows that every single thing has it's own history. The root of an Wikipedia article about something is based on the very history of that thing.
- Tim Berners-Lee: The next Web of open, linked data at TED Talks, Mar 13, 2009, YouTube - Transcript
10:17 - In fact if you're responsible -- if you know about some data in a government department, often you find that these people, they're very tempted to keep it -- Hans calls it database hugging. You hug your database, you don't want to let it go until you've made a beautiful website for it. Well, I'd like to suggest that rather -- yes, make a beautiful website, who am I to say don't make a beautiful website? Make a beautiful website, but first give us the unadulterated data, we want the data. We want unadulterated data. OK, we have to ask for raw data now. And I'm going to ask you to practice that, OK? Can you say "raw"?
10:55 - Audience: Raw.
10:56 - Tim Berners-Lee: Can you say "data"?
10:57 - Audience: Data.
10:58 - TBL: Can you say "now"?
10:59 - Audience: Now!
11:00 - TBL: Alright, "raw data now"!
11:02 - Audience: Raw data now!
Examples of lost works
- USA - The nation has lost about half of the films produced before 1950 and as much as 90 percent of those made before 1920. In addition, more and more nitrate-based and acetate-based films are deteriorating with the passage of time.” 
- en:Apollo 11 missing tapes
- en:Lost film
- en:Category:Lost works
The government can simply buy DVD's with all the movies produced every year (about 1,000 movies per year), and keep them safe, with backups on hard drives, in two or three locations. The costs would be absolutely insignificant.