1) You're quite the zero-tolerance guy, aren't you?
Except it's not that simple. Form I-9 page 1 is to be filled out by the worker within one day of starting a new job, and page 2 afterward by the employer within 2-3 days.
So you don't have time to have your immigration lawyer actually look at it, unless you got some pre-filled form, which doesn't normally happen. In fact, you fill in page one and return it to the employer for the next step.
2) Having said that, I appreciate the original blog post bringing this to my attention, and plan to be more careful with this form than the last dozen times I've signed it.
I'm pretty sharp with US employment, tax and passport forms, yet that's the first time that I've heard somebody being banned for an I-9 mistake.