王某，李某 are the words often appearing in news reports of Chinese language media, they roughly mean so-and-so if I am not wrong, but why do news media use such ambiguous terms to make news reporting? Like in an English language media, we cannot say President So-and-so of the US. How is 某 used properly with names?
～某 is only used when the person in question is one of insignificance, or when their identity is not to be disclosed (e.g. in legal documents). Such usage is either derogatory or protective of their privacy. So we may say
被告人王某 defendant Wang
*A市市長陳某 Mayor of City A, Chen
Edit (based on Tang Ho's comments): a special case is when
～某 is used unto oneself by oneself for humility. In Romance of the Three Kingdoms (三國演義), after the Battle of Chibi (赤壁之戰) where Cao Cao (曹操) lost, Zhuge Liang (諸葛亮) sent Guan Yu (關羽) to guard Huarong Pass (華容道) to ambush Cao Cao's retreating troops. Guan Yu was once under Cao Cao, but they are now in opposing camps. When Cao Cao arrived, Guan Yu said to him (humbly),
I followed the orders of my military advisor (Zhuge Liang) and have waited for you the Prime Minister (Cao Cao) for long.
Of course his letting Cao Cao go is another story.