I recently interviewed at a large company and did very well on all the questions, connected with the interviewers, had long chats with the recruiter, etc - but didn't get the job. I suspect one of the reasons I didn't get the job was the fact that I mentioned my wife/kid. The team that I interviewed for were all fairly young (so am I) but I think the kid thing could've thrown them off.
This may just be an issue at and job level that I am applying at and I'm very prepared for the fact that it may have been because I didn't do as well as I thought, but I have no idea what else it could've been. Would be great to know if anyone else has ever felt this.