Learning Viral: Is your product a natural or add-on?

Was Google Search a natural or add-on? None of them. It was just extremely useful and spread the world virally nevertheless...

evite...as much as we can't stand how it looks gets this natural virality thing going.<p>"I'm invited to a party? Well, yes, I'll rsvp and invite other cool people..."

You "go viral" by making people fans of your product, whatever it is. It's no more (or less) complicated than that.