Who did they think wrote Wikipedia? I'm not sure that much concern should be taken for people who don't care at all about the sources of the things that they reference; not that it's not bad that they'll be confused by bad information, just that if people aren't concerned at all about sources, they're going to be confused by a lot of things, not just Wikipedia vandals.

Printing something in a book doesn't make it true, and putting it on a website also doesn't make it true, no matter how professional and authoritative-looking the css is. You trust something because you trust the motivations and expertise of its sources.