[subverting]

What's the problem if it isn't made yet?

This is a better strategy, see if theres a big enough market. They're also building the list so that their launch will be good and they don't have to spam it everywhere else, they just alert the people who already expressed interest.

There's nothing wrong with finding demand first, smart startups do this all the time.

[ColinWright]

Personally, I'm thoroughly fed up of the tactic. So many things look interesting, and then never see the light of day. Once bitten, twice shy, I don't bite any more.

Speaking with some of my friends and colleagues, I'm not the only one.