I find it interesting the number of responses that had success after gathering e-mails. If your 'Show HN' asks for an e-mail here, everyone gets incredibly angry and lets you know they stopped looking at your product right away.
See for example the disproportionate number of comments on HN from users who disable Javascript and or (all) cookies and remark about a site experience based on it (can't read article, some aspect not working, etc), yet from general statistics represents a niche minority.
(Which isn't to say that any such critiques are invalid either, just an observation on perceived audience)
* Good: That side of HN is within the target for a little niche Web site I plan to launch in a few weeks.
* Bad: I used a Web framework that requires 10x the hosting resources that it should (resume-driven-development), so I might have to upgrade from free-tier hosting before HN mention, just to not be embarrassed by hug of death.