Good idea:
Making your own framework so you have control over it and your projects

Bad idea:
Making your own closed framework rendering Google and SO useless

Context: the company I work for creates their products using their own framework, it works well and allows for things other framework didn't think about, any error coming from it cannot be searched for since it's only used internally.

Good Idea: Code Reviews

Bad Idea: Code Reviews before your first sip of coffee.