The science articles are usually safe on wikipedia, because it is hard to politicize the properties and observations of, say, uh, VY Canis Majoris. People on wikipedia are usually very good about these sorts of articles.
Cultural or political articles are the worst, however: everyone with their "unique" point of view comes on wikipedia to pound their drum. A person of A ideology makes X citation here, while a person of B ideology makes Y citation here arguing against X but never decisively, and it simply becomes a clusterfuck of whiny voices trying to outdo everyone else. Not balanced perspectives.
Don't believe me? Try being a wikipedia editor sometime: it becomes a game of reverting opposing edits and navigating the role-playing bureaucracy of the site. And while it is theoretically a good thing that can happen, some idiot will come around eventually and do the same to you, and eventually you will get into some utterly moronic "arbitration" game that requires no social life or hobbies whatsoever.
And then there is the scandal of essjay, one of the most abusive admins of wikipedia history, only to end up to be revealed as a fraud who used fake credentials under anonymity to abuse other users into accepting his dogma.
Then there are more contentious points that could never get resolved because of the "mainstream" versus "esoteric" knowledge(s) on various subjects. Take Metallica, for instance: they're listed as a highly influential metal band, though it is debatable of how unique their contributions actually are/were. Perhaps they popularized certain stylistic characteristics, but were they really the ones influencing others if they were primarily influenced by others, for the most part? Sorry if that is vague, I can't think of a better example that is more obvious. But the problem is that wikipedia will never actually accept what *actually* is, but on what is group consensus, because no original research is allowed; thus, what most people believe is true is true in wikipedia's eyes.
It is fine if you disagree with my example, but the concept of what I'm saying is still valid.
And to end on a positive note: "deletionists" are some of the most worthless people that one can find on the internet. They get their jollies off of deleting as much as they can, despite the site being more useful if it contains as much truthful information as possible.