I am sick of sitting behind people at stoplights and seeing them eyeball me(when they're not fixing their makeup or hair or whatever) in their sideview mirror.
If you can look in your sideview mirror and see along the side of your car, and see the person in the car behind you, your mirror is not adjusted properly, and you have a gie-normous blind spot.
When a vehicle disappears from your rearview mirror, it should have just appeared in your sideview mirror, and vice versa.
I have never yet seen, since I moved here, a person with their mirror adjusted correctly. This probably explains why so many of them slide over into another lane, oblivious to another car already there.
Well, maybe the mirrors and the fact that so many of the drivers don't care in the least what's behind or beside them....