I rarely get asked to sign NDAs for doing dev work anymore, but it happens occasionally. I'll often find they're less an NDA and more a non-compete that's been sent as an 'NDA'. They're usually vastly broad "you won't work on anything like whatever project we're working on for 2 years" - or similar, which is ridiculous because a lot of my work is much the same or for companies who are (broadly) competing.