Why delete unsourced material? I often delete material which has been templated or tagged as unsourced for long periods of time. I usually don't try to find sources for the material. For one thing, that was the duty of the original authors: it is inappropriate to add material to Wikipedia without citing a reliable source.
But there is another reason which has to do with the nature of Wikipedia, and the stage at which the project now finds itself. Wikipedia is full of articles which either lack sources entirely, or have very poor sourcing. These articles were typically written years ago, and no one currently pays attention to them. They may have valuable information... but they may be inaccurate or misleading or outdated.
Wikipedia is a project in decline. It may be just as important as it used to be, but the work of refining and sourcing minor articles on obscure or unpopular subjects is unlikely ever to continue -let alone be completed- on many articles. Wikipedia aspires to be reliable. As the number of editors willing to source and maintain obscure articles declines, Wikipedia must choose between achieving its goal of reliability and retaining much of its text. Formerly, one could pretend that obscure articles would at some point be properly developed, edited, and sourced. This is no longer the case, and we need to prune unsourced or unreliably sourced text from our articles. I consider this a noble effort to increase the reliability of the project. Others may consider it "deletionist" or simply rude. But I submit that in the long run, given Wikipedia's goal of reliability, it is absolutely necessary to the project.
- "There seems to be a terrible bias among some editors that some sort of random speculative "I heard it somewhere" pseudo information is to be tagged with a "needs a cite" tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information..."
- "I think a fair number of people need to be kicked out of the project just for being lousy writers.[1]" -Jimbo Wales
Notes
edit
Please boldly add information to Wikipedia, either by creating new articles or adding to existing articles, and exercise particular caution when considering removing information. However, it is Wikipedia policy that information in Wikipedia should be verifiable and must not be original research. Please show that information is verifiable and not original research by referencing reliable sources. Unsourced information may be challenged and removed, because on Wikipedia a lack of information is better than misleading or false information—Wikipedia's reputation as a trusted encyclopedia depends on the information in articles being verifiable and reliable. To avoid such challenges, the best practice is to provide an "inline citation" at the time the information is added (see: WP:Citing sources for instructions on how to do this, or ask for assistance on the article talk page).[3]
Other people have to be able to check that you didn't just make things up. the nutshell of wp:v
The burden of evidence lies with the editor who adds or restores material. You may remove any material lacking a reliable source that directly supports it. How quickly this should happen depends on the material and the overall state of the article. Editors might object if you remove material without giving them time to provide references. It has always been good practice to try to find and cite supporting sources yourself.[4]
Any material that is challenged or likely to be challenged must be supported by a reliable source. Material for which no reliable source can be found is considered original research. The only way you can show your edit is not original research is to cite a reliable published source that contains the same material. [5]
 | This article possibly contains original research. |
Uses the same language as the
 |
template
Also the templates make clear that "Unsourced material may be challenged"
Does every single sentence need to be followed by an inline citation? No. Only four broad categories of material need to be supported by inline citations. Editors need not supply citations for perfectly obvious material. However, it must be possible to provide a bibliographic citation to a published reliable source for all material. from the header of wp:v
Ah, finally, this says that a fact tag is a challenge:
http://en.wiki.x.io/wiki/Wikipedia:MINREF#When_you_must_use_inline_citations
If a claim is doubtful but not harmful, use the [citation needed] tag, which will add "citation needed," but remember to go back and remove the claim if no source is produced within a reasonable time.[6]
http://en.wiki.x.io/wiki/Wikipedia:Citing_sources#When_and_why_to_cite_sources