Yipes! I was sorting out users earlier today since some shady folk use bots to create lots and lots (like hundreds!) of accounts just to spam your typical viagra-links in their personal info are (what a useless thing to do).
I deleted all of those fake accounts and thought I'd set a trap, any user that hasn't logged in (that is, hasn't logged in at all) is pretty much either one of those accounts or someone who misspelled their email - either way said account should be closed I reckon. So I set a widget to email and then block any user who hasn't logged in (at all), but the widget must have misunderstood me because it pretty much took my instructions to mean anyone who hasn't logged in in the past two weeks. Oh Noes!
I spotted what was happening and managed to stop it, but only after a huge chunk of those emails already had been sent out. Aaargh. So sorry - I'm turning that widget off and never looking at it again, promise! I'm really sorry about that.
As for the spammers, our new prove-you-are-human device will weed them out. ;)