Let people know what you're doing so you know if you're doing something worthwhile. Remember: if they don't get what you're doing, it's certainly not their fault. Don't get haughty and cry that they're not sharing your vision. Let a potential user tell you what they want.
good point. harnessing user intelligence not eyeballs ~ http://news.ycombinator.com/comments?id=5886
I just hope this still remains the case with SO many applications (most with solid demos I imagine..). Its probably very easy to get lost in the sea of impressive startup demos.