[viiralvx]

Not OP but I feel like it's because JavaScript has evolved enough that some of the niceties they offered before doesn't make sense. I like using Ember.js and doing client-side validations is pretty darn easy without complicated JS. Additionally, having inherited a legacy Rails project that uses `remote: true` in it's forms, it is causing more of a headache to fix these legacy issues.

[senko]

Validating data should always be done on the server. You should never, ever, trust the client.

That's not to say you can't do (or shouldn't do) form rendering, processing, error/success handling, etc. on the client-side, but the server should always have the last word on the validity of what you send.