I make them all the time.
Once I meant to say that someone had been "missing for six hours" and somehow I hit the P key instead of the M.
Another time, on a thread about an especially cruel sentence in Nigeria, I meant to type "It's tough being an old woman in Nigeria" but for some reason it came out as "It's tough being on old women in Nigeria".
But I don't expect people not to laugh when I present them with comedy material.
I'd also be real careful to proofread when selecting a permanent screen name, but maybe that's just me.