Of all the things I learned in during my MBA, the strategic importance of the network effect is the one I see most misunderstood in the tech industry.  The network effect is present when the value of the a product or service is in large part determined by the number of other users of that product or service.  EBay is perfect example of the network effect.  Creating an Internet auction site is not very difficult and is an extremely lucrative business.  EBay had a gross margin of 74% in 2008 because the business never handles physical goods and the cost of running any auction marketplace is low.

So why does EBay have no serious competitors in the US?  Amazon tried to break in to the auction space without success.  EBay’s competitive advantage is the network effect.  If I want to sell something, all the buyers are on EBay.  If I want to buy something, all the sellers are on EBay.  Moving to another site as a buyer or seller means I’d lose value since all the other participants are not there.  Thus an auction site could be better than EBay and cheaper or even free and still not succeed because the value for either party is driven by the presence of the other party.

The principle applies to Craigslist as well.  It would not be difficult for someone to build a classifieds site with better features than Craigslist which still looks circa 1999 .  Web technology has advanced considerably in the last decade but Craigslist is in a time warp.  When I look for furniture on Craigslist, it’s incredibly annoying that I can not see my search results with pictures without having to click through to every listing.  However, I do not use a more functional classifieds sites since the number of listings is too low to be useful even with better features.

Facebook also benefits enormously from the network effect.  Social networks are useless unless your friends are there.  Since Facebook is the largest and almost ubiquitous in some circles, the only general purpose social network it makes sense for people to join is Facebook.  Thus, social networking is very likely to have an industry structure similar to Internet auctions where one player dominates and the 2nd and 3rd place players are dramatically smaller.  To counter the network effect, the smaller networks like My Space have to carve out a defensible space where Facebook can not effectively play for some reason.