This would swing the balance too far in favor of the deletionists. The unsourced statement would have to be unreasonable. Obvious common knowledge statements should not have to be sourced, and someone edit warring, demanding that every petty statement be sourced is being unreasonable, and should not be rewarded by being allowed to impose a burden upon other editors. -- Silverback
The simple solution to someone edit warring demanding that a statement be sourced is to add a reference at the bottom of the article. If the statement really is obvious then it should be simple to find a source.
Yes, someone gaming the system by removing something which they know to be true rather than just adding the source themselves should be reprimanded. But at the same time, a better solution than edit warring with that person would be to just add the source.
I don't think anyone's claiming that you have to cite sources for every fact within the main body of the article. I don't think [1] that articles [2] should look [3] anything like [4] this. [5] Rather for something "obvious", it should be enough to cite the source at the bottom of the page.
I'm saying all this as though it's a proposal, but it's really already policy. See [[Wikipedia:Verifiable]], especially #Checking content.
Anthony