What is a gimmick? Are gimmicks really negative to the industry?

[Never]

I think the term is thrown around far to much. People have started to use the word gimmick when talking about basic gameplay mechanics.

There should be some sort of law, like godwins law, that says that if anyone uses the term gimmick in regards to the subject of computer games they're a silly billy, or something... Not really got that law in a finalised state yet. Needs some work.