My favourite, rightly placed at the top of the list:
- Have at least one very clear, and cool, use case. I.E. have something you can show someone else that makes them say "oh, my, that's freaking useful."
This is true for all startups. You gotta have something magical, and you gotta know what it is and make sure your users see it.
Worth bearing in mind that this is Scoble's opinion, rather than any sort of rule of law, and most of those tips could help many startups, when mis-applied they could really hurt them too.