Agree with the comments about talking to users and doing things that don't scale, which is some variation of #1.

Also learn as much as possible from the lessons of similar projects that failed. The one that came to mind is Flowtab.

http://techcrunch.com/2013/08/31/the-decline-and-fall-of-flo... HN discussion: https://news.ycombinator.com/item?id=6307068