A study of Facebook apps has shown that people are more likely to buy a product if it's already very popular - but that a clear winner that doesn't reach a certain popularity threshold won't benefit from this effect.
The observations could be of interest to companies such as Amazon and Netflix, which already allow their users to rate their products. It implies that positive user reviews will only give a big boost to a product's sales if it's already popular.
The Oxford University researchers analysed data on 100 million installations of Facebook apps, checking on an hourly basis the rate at which they were installed.
They discovered that once an app hit about 55 installations a day, its popularity soared. While a typical app was installed by 1,000 users, the most popular app, 'Top Friends', was adopted by 12 million.
The study puts the difference down to social influence - crucially, when the data was monitored in 2007, Facebook friends would always be notified if one of their online friends adopted a new app.
All Facebook users could also see a list of the most popular apps – similar to best-seller lists – so knew how the global community, as well as their own friends, rated the apps.
"Our analysis reveals a very interesting new finding. Users only appear to be influenced by the choices of other users above a certain level of popularity, and at that point popularity drives future popularity," said senior researcher Dr Felix Reed-Tsochas.
"Below this threshold, the effects of social influence are imperceptible."