Any time you make an error like that you should immediately change your password anyhow. But I guess some people like to live dangerously.

One thing that really doesn't help here is that Unix password entry traditionally hides the input text completely, instead of showing bullets. Normally you would notice pretty quickly if you're typing in the wrong place, since nothing is showing up where you expect it, but Unix terminals train users to expect no feedback when typing passwords, so they're more likely to type the full thing and press enter before noticing anything is amiss.