This. Have done this for my own and in some cases friends' potential startups: a fake door landing page and a couple hours of posting to discussion groups (don'

This. Have done this for my own and in some cases friends' potential startups: a fake door landing page and a couple hours of posting to discussion groups (don't spam, do it where communities allow) or a small Google ads advertising budget. There's been a couple cases where that simple amount of initiative plus about a half day of work, the resulting feedback was enough of a push to overcome hesitations my friends' had in starting a company.