In my experience, making obviously bad things difficult or impossible improves reliability. This idea certainly resides within my cranial cavity, but that doesn't necessarily make it wrong.
The obviously bad part is that you pollute the global namespace for no reason other than laziness. When someone comes across code that uses a "Table" object interchangeably with "Dictionary" and "Hash", then he's going to have to look through the source code to find this bizarre line only to find out that you renamed a built-in container for no good reason.
