Although, to be fair, in the strictest sense of what he said, it still stands correct. None of the examples you have given hold up to the rule. All of the sites (Google, Facebook and YouTube) are not in a 'perfectly competitive' market due to network effects (even though Google and YouTube deny this).

If they were, none of them would own 60% of the total market. There would be many more market participants and there would be no barriers to entry. That's what he was referring to.

In a market where there are no barriers to entry (i.e. perfectly competitive), the long-term price will tend to zero.

Now that I am thinking about it, even though the internet is 'free', and has very low barriers to entry for some businesses, I can't think of an example of some sub-industries (search, social networking, video hosting, etc.) online where the market is perfectly competitive. There is always an inherent advantage and some outsized competitor, relative to everyone else.