I imagine a launcher which hashes the binary before you run it and compares the hash to some kind of registry. Then it can tell you that 5 people you explicitly trust have encountered this hash, and 768 people that they trust have, and 5789 people that they trust...
If you're the first person to encounter the hash, or if the number of hops is very high before you encounter something besides 0 (eventually heading into sybil-territory) then you have cause for extra scrutiny.
Bonus points if the people who developed the app are participating, but still useful if they're not.