Re: moving functionality from the server side to the client “brings its own security challenges”.
Totally agree - validation etc. on the client is purely to help improve user experience; it needs to be replicated on the server to be any kind of guarantee that it's doing what was intended. And yep, I also agree that there are too many inexperienced web developers out there who don't appreciate that. I'm being polite and swapping "inexperienced" for "idiot" :)