It is exactly an options contract! But OP wants to write a short on a stock that isn’t on the market yet. Which brokers do you recommend that allow this kind of trade?

Yes but you’d have to find a buyer yourself and write a contract to sell them shares - the brokerage won’t do that for you.

Also interested if Yahoo! Mail will be doing this with their “pay for non-personalised adverts” thing - are they going to be giving all these profiles to advertisers (e.g. foreign intelligence agencies) as part of the “bid for an advertising slot” process? (even if your adblocker then hides that advert)

China’s already got control of that!