Think of it as your Klout score, but instead of measuring social influence, it’s a aggregate score of your reputation across various collaborative consumption platforms. Implementation wise it can be as simple as an automatic crawler that collects these statistics from the public profiles from each platform, or having each platform adhere to a standard set of rest endpoints returning the scores for each user in the platform.
It would be a place where people can find out whether you trashed your last AirBnB room, whether you returned the car in proper condition on iCarsClub, whether you provided accurate description on RentTycoons, or even if you did return the items you exchanged on Leendy by the stipulated time. In time, this score might be as, or even more, valuable than your social influence score. Especially when Collaborative Consumption isn’t a trend, it’s a way of life and it’s here to stay.
The score itself might be represented as a percentile within each system. e.g. if the user’s rep is above 75% of all users in AirBnb, his component from AirBnb would be 75, etc. Then each component from different platforms would be normalized by the the number of actions/transactions made on each system, and in time it may be modified with recency as well.