What is a social product? This was the question Sandi MacPherson, founder of Quibb posed to me, over lunch earlier this week.

In Startupland, we bandy about terms like social, social media, virality and community when talking about products but it wasn’t until that moment that I stopped to think a bit more about what each word really means. Sandi has thought a lot about these concepts while building Quibb and she has some of the clearest points of view on social products I’ve encountered. These are my notes from that conversation:

Social Social products have three parts: product (the technology), means of user acquisition/growth (virality) and community (people). The first part, the product, has three features: user profiles, a relationship metaphor (follow/friend) and some kind of data stream/feed for content sharing.

But just building a product with these three features isn’t anywhere close to enough to be successful. Next, the service needs to grow.

Viral The most natural growth mechanism for social products is through the network itself. This is virality. Viral products use invitation systems to grow quickly. Invitation systems include Facebook Connect, refer-a-friend like Dropbox or team/clan structures like World of Warcraft. Virality is a marketing tactic.

Virality belongs to the same category as SEO, SEM, content marketing, affiliate channels because it’s a customer acquisition vector. Virality differs a bit from these others because successful viral acquisition requires deeper product integration than most advertising. Nevertheless, virality is a marketing tactic, one that is increasingly a science.

Community But product and viral growth still aren’t enough. The least well understood, documented and discussed but most important element of social products is community. Community is the x-factor.

Communities aren’t products or part of the product. They are amalgamations of people who interact with each other in a certain context and a kno