That's true, and good advice. I tell people straight up when I interview at startups that I value their shares near zero until/unless they can prove to me they're not. If they can't, that's fine, and I'll apply a significant discount no matter what, but my base salary need to be accordingly.

For starters, in any early stage startup I'd discount by 90%+ just because it's a startup, entirely irrespective of whether I like the idea, and what investors think.