This sucks, but it's not accurate -- in both directions. Offer letters can get broken too, and legitimate offers don't always come in the form of offer letters

This sucks, but it's not accurate -- in both directions. Offer letters can get broken too, and legitimate offers don't always come in the form of offer letters. I've both taken employment (including flying thousands of miles, one way, etc.) and offered employment on handshake basis, although usually with terms in email just so they're written down. Big companies do offer letters via HR and some formal process, but there's no fundamental difference between email from an authorized party offering something. vs. a scanned PDF attached to an email. You need to show the elements of contract were met, but the form doesn't matter -- email is a big step up from verbal contract, which also exists. The real rule is: don't do work for lying assholes. If you can't trust your counterparty, you need a lot of compliance and enforcement machinery, and that's usually well beyond what an individual employee can bring to bear.