I am totally *not* a "keeping up with the Joneses" type person, and I really couldn't care less what other people have and do compared to me....etc.
HOWEVER! Like lots of you have mentioned....it's reeeeeally hard not to notice when someone seems like they're trying to BE you! And yes, that is ANNOYING!
A few years ago I had an acquaintance (ex-friend type situation) who was doing that to me, and it bugged the crap out of me! I have a really unique style sense, and everyone jokes about how I change things up all the time, never look like anyone else, etc. I don't deliberately do it to be "different" from everyone else, but I enjoy being creative and a bit of a free-spirit, and it was nice feeling like I had my own personal trademark "look".
Until this girl started copying everything I did!
If I wore a certain combo of skirt/shoe, guess what....next week, she wore the same kind of outfit. If I changed my hairstyle, she showed up with the same style. Etc. etc!
It was a funny situation, because she really didn't even LIKE me, but on some level she seemed to want to BE me. I don't even know if she was doing it consciously. I guess it was just a sign of insecurity and not having her own identity, because thank goodness eventually she transferred her obsession to someone else and started copying HER!