Why not?

It fits the definition from the article. “An industry in which high infrastructural costs and other barriers to entry give the largest supplier in an industry an overwhelming advantage over potential competitors”

In case of FB the infrastructural cost is less of an issue, at least not anymore. I think Amazon and Microsoft are capable of hosting at least a dozen Facebooks each on their clouds should they want to. The main barrier to entry which causes that overwhelming advantage is network effect.