Technical challenges aside, here are a few major problems with having this type of reputation measure for everything:
* It's a huge invasion of privacy. There's a reason why credit ratings are difficult to access.
* It's uni-dimensional. Some things don't measure that way, it's why the word "trade-off" exists.
* It's a serious limitation for the sub-optimal people/businesses out there. How will the socially-awkward people find dates? How would new businesses be able to make the necessary mistakes they need to in order to find a market fit without seriously damaging their information?
* How do you avoid people gaming the system to become more "reputable"? See https://www.google.com/search?q=why+I+left+stack+overflow
* It's a major hurdle for those who do not yet have any reputation: those who are from outside the system such as new businesses, or don't know the system such as new immigrants and non-early adopters.