The quote is right. The only enemy of your startup is yourself. MySpace fucked up in so many ways that it's surprising that they managed to remain somewhat relevant until around ~2010 or so.

The point is that you're very unlikely to get to that spot, and you don't have to think about that in the beginning. And even then, if you focus on your own company and execute well, you generally don't have to worry about your competitors - it's yours to lose.

One example is not indicative of the larger picture

App.net lost to Twitter. Netscape lost to Microsoft. Yahoo lost to Google. Ouya lost to Sony, Microsoft, and Nintendo. Coin lost to existing payment cards...

The sentence that follows the quote is "So unless you discover a competitor with the sort of lock-in that would prevent users from choosing you, don't discard the idea.". Most of the winners in the examples you gave had insurmountable lock-in (network effects, etc).

App.net lost to itself. I know of exactly one person who decided to pay money, and it's my friend who'd buy/try anything once.

Try to charge money in a space that's free, in return for..... I don't really know tbh, is a recipe for suicide. It may have worked in the 2 weeks of the novelty effect, and that's it.

There was a period of time where I used both MySpace and Facebook, and preferred MySpace – but the user experience kept getting shittier, it kept getting laggier, spammier... MySpace killed itself

Also how MySpace failed to defeat Friendster.

Did you listen to the recent Startup podcast series on Friendster? The folks at Friendster definitely saw MySpace as one of the nails in their coffin.