You just give your boot size, that's more than enough to mount some bindings, then you adjust yourself if necessary. (It just takes a flat screwdriver and one eye)
Besides the fact that you have somebody to physically yell at if they screw up, I don't really see what's better about having a local shop mount them, I mean they have no more interest in screwing it up than a local shop does, right?
They basically have the same job, and I don't see why working in a ski-shop would make you any better and prevent any mistake.
A few weeks back, a kid posted about how his local trustworthy ski-shop screwed-up his bindings twice or something. So shit happens, people can make mistakes, but if you use a professional website with good reviews and feedback, no reason to worry.
But if you know somebody you trust working in a ski-shop, known as the Tammy Wallnuts of binding mounting, then you should obviously ask him, but I assume you don't, or you wouldn't be making this thread.
In this particular case, I'd say the only reason for you going to a local ski-shop instead of asking the website to do the job is if you think meeting with the guy who's gonna do it will make him be more conscientious because he saw you in person. In my opinion it won't, and if you can save a few bucks..
Just my 2 cents, correct me if you think I'm wrong.
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