Keep in mind that requiring users to sign up before trying the product contaminates user count as a meaningful metric, and devalues it as a marketing channel be

Keep in mind that requiring users to sign up before trying the product contaminates user count as a meaningful metric, and devalues it as a marketing channel because it's filled with unqualified non-users. I totally hear you that it sucks when you know people try your product but leave without signing up, and worse still you have no channel to ask them why. Users exploring a public demo have shown real interest in your solution to problems they have, and while they're exploring (especially if the demo is somewhat guided) there's a very natural opportunity to begin a conversation without requiring a signup. Ask for feedback (via survey, olark chat, quick submit comment form, your contact info...), offer to email product updates or tease future enhancements, show you twitter feed, etc. Moving registration downstream doesn't have to mean you can't learn about potential customers.