[Macha]

Not so sure about that, people unable to spell YouTube seemed to do more harm to Universal Tubing who owned utube.com than it did YouTube. If you hadn't heard of them before, how many ts in Twitter? Is TikTok spelt with the letter c?

[bamfly]

People who've seen YouTube written down a couple times tend not to get it wrong. Twitter is a common dictionary word and I'd bet had a pretty low misspelling rate, if you'd asked people to spell it before the service Twitter even existed. TikTok, I think most people get after seeing it a few times, at worst.

Mastodon? It's a dictionary word, so it as that going for it—and yet, people see it a hundred times and still often misspell it. The pronunciation's just a bit too far from the spelling, at least in American English. Most folks say it as if it were spelt "mastadon", especially if they're not trying to enunciate carefully & precisely and (perhaps) don't know the correct spelling.

(I'm not weighing in on whether that's some kind of serious problem for Mastodon, but I do think it's worse than all your other examples, as far as likelihood of misspelling even after significant exposure—then again, web search smooths over most of that, for anything sufficiently popular)