Quote from dmo:
Right, that's what I said - " If you do it in such a ratio that you are vega neutral" - which equals gamma neutral and theta neutral provided all your options have the same expiration date. That means being long more wings than you are short the middle.
Naked long straddles are completely different in that they are pure long-premium plays. Every day that the underlying doesn't move you lose money - more today than yesterday, and more tomorrow than today.
But if you start off short the middle and long the wings at a ratio that makes you gamma, vega and theta neutral, then if the underlying doesn't move, you get shorter and shorter premium (make more and more money) every day. If the futures DO move, you get long premium, which is usually just what you want. So this position has you short premium if the underlying doesn't move, and long premium if the underlying does move. It has you short premium if IV goes down, and long premium if IV goes up. These are exactly the characteristics you want in an option position. It is a very, very comfortable position to have. But comfort comes at a price. That's why those wings are expensive.