>It's all a question of timing, of course. If you buy a
>put option and the bubble keeps going while your puts
>expire, you've lost money for nothing. You can keep
>buying more puts but, if you've been doing this for the
>last year or two, your transaction costs may well
>exceed eventual gains.
>
>Or you can sell short, in which you borrow a stock,
>sell it, and promise to repay the debt by replacing the
>stock at a later date.
Here's a technique that is only for the strong-stomached & well-capitalized: sell call options naked (i.e., without owning the underlying stock) against, say, the Philadelphia exchange's Internet (DOT) index. If the market goes against you, roll up (sell the next higher strike price) and double your position. If it goes against you, roll up & double again. Sooner or later, the market will go your way, and you'll pocket all the call premium. Of course, you may be on the hook for about $4 billion if this continues...
Doug