In our editorial policy, we treat the web as a publication medium like others. We don’t give it special treatment unless something inherent in the medium calls for doing so.
Titles of free-standing works in print are italicized, and so are such works on the web. This policy is clear-cut for online works with a single author like People of Color in European Art History. Other sites, like Wikipedia, have a collective authorship but are unified works all the same. Further out on the spectrum, a site like Facebook has no unifying authorial mission: it’s a template filled by independent authors. Yet all authorship there takes place under a heading, Facebook, and the constraints of the template give a character to the content, however minimal.
A good editorial policy should be simple and not demand hairsplitting by writers, editors, or readers. Typography offers few tools for conveying conceptual distinctions. We think that the least vexed approach is to use a single format for all three titles above (and the titles of all other websites). To argue that Facebook is fundamentally unlike the other two would require a definition establishing the difference—a definition that can clearly divide all other sites into one of the two categories. The definition would be endlessly debatable, given all the variations in online publication.
There are also practical benefits to italicizing Facebook, Google+, and so on. The italicization results in more readable prose in a tech-heavy discussion that includes many unitalicized capped terms (acronyms, trademarks, names of companies). Further, the style allows for typographic distinction between titles of sites and similar names of companies. Just as italics helpfully mark the difference between The New York Times (the newspaper) and the New York Times Company, so they allow a useful distinction in “a posting on Facebook” versus “the CEO of Facebook.”