Sure every once in a while its possible for any one to drop in a spelling mistake, but those are rare situations in code. Mostly because code is often not a dead piece of documentation, which is read and auto corrected in the human brain. Code works on a computer with well defined interfaces and protocols.

Think of it this way, would you hire a programmer who often makes typos, to write shell scripts that have 'rm -rf'?

If you wouldn't, how often do you trust these people to execute DROP DATABASE <typo_database_name_which_happens_to_be_real>?

There is a big difference between programmers who can put in typos in a sentence in a code comment, and the kind of ones we are talking about.