You might gain some trust in a team which maintains a particular PPA. You import their key manually, and the key is not auto-updated or anything. Installing sh

You might gain some trust in a team which maintains a particular PPA. You import their key manually, and the key is not auto-updated or anything. Installing shareware windows apps from "random sites" seems riskier, they're not signed by a single uploader's key which you import just once.